Luminous Landscape Forum

Equipment & Techniques => Cameras, Lenses and Shooting gear => Topic started by: Ray on November 11, 2010, 01:56:22 am

Title: Nikon D7000 Dynamic Range
Post by: Ray on November 11, 2010, 01:56:22 am
We probably all know by now that the DR of the D7000 at base ISO (together with that of the Pentax K-5) trumps every other digital camera on the market, whatever the format.

The P65+ is a laggard and under-achiever compared to the tiny format D7000, as regards DR.

But before you go purple in the face with rising blood pressure, and release yourself into an explosion of expletives directed against DXO, let's consider for a moment what the DXOMark rankings really mean.

I think many of you may have bravely ventured beyond the single-figure rankings, and dared to examine the individual graphs comparing one sensor with another of your choice.

If you have, you will likely have noticed on the top left corner immediately above the graphs, there's a (screen-print) option.

When you toggle between these two options, you should notice a substantial change in the results, on the graphs.

With the option 'screen', you are comparing the qualities of one pixel with another (for example, a D7000 pixel with a P65+ pixel).

What the DXO results tell us, is that the P65+ pixel is pretty much the same as the D7000 pixel with regard to SNR at 18% grey, tonal range and color sensitivity, at base ISO. Above base ISO, all bets are off. We sink into the abyss and the P65+ flounders.

However, most images are composed of all, or most, of the pixels on the sensor, depending on the degree of cropping. If we want to know what the comparative image quality would be like, if we were to downsample the P65+ image to the same file size as the D7000, for example, then hit the 'print' option.

You should see a significant jump in the image quality parameters for the P65+. The D7000 still retains its DR supremacy, but takes a dive in all other qualities (SNR, tonal range, color sensitivity).

Now, at this point, I think some further explanation is required about the 'normalisation' size in 'print' mode. It's specified at only 8mp which represents a print size of 8x12 at 300 dpi.

That seems a bit on the small side. I don't imagine that P65+ owners will often make prints that small. Is that size relevant?

Well, yes it is. DXO have chosen that small size in order not to exclude too many camera models. Any image consisting of fewer than 8mp would have to be interpolated.

Here's what DXO have to say on the matter.

Quote
Original measurements are useful to help gauge the actual image quality when viewed at 100%, but they do not predict how printed images will compare. In order to give a better prediction of how prints compare, a normalized version is more reliable and is provided based on 8Mpix

And this is what they have to say about the 'single-figure' rankings.

Quote
Sensor Overall Score is normalized for a defined printing scenario—8Mpix printed on 8”x12” (20cmx30cm) at 300dpi resolution. Any other normalization, even with higher resolution, would lead to the same ranking, given that any camera that could not deliver the chosen resolution would be eliminated from the comparison.

In other words, whether a P65+ image is downsampled to the 8mp of the Canon 20D, the 24mp of the D3X, or the 16mp of the D7000, the ranking is unchanged.

So we should bear in mind that DXO do not offer rankings for small format cameras uprezzed to the higher pixel-count size of larger formats. This seems to me to be at the hub of the confusion.

I think perhaps DXOMark should place a big sign above their single-figure rankings, such as:

These rankings apply only to images that have been downsized to the native print size at 300 dpi, whatever that may be according the pixel count of the smallest camera in the comparison.

Okay! Now to the issue at hand. It seems that some cameras are extremely good at high-ISO performance, but average at low-ISO performance, such as the Nikon D3s.

The D7000 seems to be very good at low-ISO performance, DR-wise, but pretty average at high-ISO. It seems we can't have everything, although we may want everything.

With regard to every parameter that DXO test, except DR, the P65+ is streets ahead. No question.

So what is the significance and the benefit of such high DR, at base ISO, I ask myself? How does it translate to improved image quality?

I found it surprisingly difficult to find any comparisons on the internet that address this issue. But after some searching I did come across a few images that might provide some indication of this extraordinary DR of the D7000.

I'm assuming here that for editorial purposes I am not infringing any copyright. If I am, Michael will probably send me a PM.

The images are from http://robertbromfield.com/nikon-d7000-review-and-impressions/

The image I've selected is a shot at F8 with the Nikkor 14-24/2.8 at 14mm, which becomes 21mm on the DX format.

Robert complains that the image seems less sharp than the same lens on the D700. Does he not know that the 14-24/2.8, at 14mm, is sharper at F2.8 than at F8, as well as being sharper at F4 and F5.6, than at F8?

To compare the D7000 with the D700 using this lens, one should be comparing the D7000 at F8 with the D700 at F12.

Okay! To the nitty gritty. If the D7000 really does have such fantastic DR, then the shadows in Robert's night shot should be relatively clean.

We don't have comparisons with the P65+, or any other camera, so this exercise fails at that level. Can't be helped!

But at least I hope I have successfully defined the issues. The D7000 shot at night without flash, really does seem to show a remarkable amount of detail in the dark shadows, which is precisely what a high DR means.

Here are the images. First, the full jpeg unaltered; second the same image lightened in Photoshop using shadows/highlight tool; third a crop of the bottom left corner after lightening the shadows; fourth, a 100% crop showing the shadow cut-off point where all values are the same.

I'm not a particularly technical sort of guy, compared with others on this forum, such as BJL, but I've read that Nikon have a habit of clipping black levels at a certain point to obliterate objectionable banding and noise, unlike Canon who reveal such banding. Astronomers prefer Canon for this reason. Sometimes, very degraded detail is better than no detail, but probably not for most practicing photographers.

If the next iteration of the D7000 gives us 16 EV of DR, then those grey/black patches should reveal some detail.  ;D
Title: Re: Nikon D7000 Dynamic Range
Post by: stamper on November 11, 2010, 03:50:45 am
I am sitting wondering what all this guff has to do with photography? Ray do you ever spend time taking photographs? :) ;) ;D
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 11, 2010, 04:49:30 am
I am sitting wondering what all this guff has to do with photography? Ray do you ever spend time taking photographs? :) ;) ;D

Of course I do, stamper. Since the advent of digital photography I've accummulated enough photos, mostly in RAW format, to keep me busy for 3 lifetimes, processing and reprocessing the images according to my changing taste and the progressive developments in software.

Quite a few of those images would have been of high contrast scenes in rainforests, for example, where a D7000 would have been ideal.
Title: Re: Nikon D7000 Dynamic Range
Post by: Graystar on November 11, 2010, 07:53:39 am

Okay! Now to the issue at hand. It seems that some cameras are extremely good at high-ISO performance, but average at low-ISO performance, such as the Nikon D3s.

The D7000 seems to be very good at low-ISO performance, DR-wise, but pretty average at high-ISO. It seems we can't have everything, although we may want everything.

Low ISO DR performance depends on how much light the pixels can suck up (called saturation.)  High ISO performance depends on sensor area and control of read noise.  Cameras of the last couple years have very low read noise.  So it makes sense that sensors of the same size have similar performance at high ISO.  I’ve compared ISO 3200 images from the D90 and D7000 and they pretty much look the same.  The D90 actually has lower read noise than the D7000 at ISOs 1600-6400, which is why its DR matches or surpasses the D7000 at those sensitivities.

So what is the significance and the benefit of such high DR, at base ISO, I ask myself? How does it translate to improved image quality?

I found it surprisingly difficult to find any comparisons on the internet that address this issue. But after some searching I did come across a few images that might provide some indication of this extraordinary DR of the D7000.

I’ll bet that you don’t own a recent Nikon.  From a dark area such as your crop, a Nikon owner would expect to be able to bring out that much detail.  The D7000’s DR boost comes from having a higher pixel saturation point, as well as lower read noise at low ISO.  To see the expanded DR in action you need a scene with a large DR, such as an indoor shot of a window on a sunny day.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 11, 2010, 08:39:15 am
Low ISO DR performance depends on how much light the pixels can suck up (called saturation.)  High ISO performance depends on sensor area and control of read noise.  Cameras of the last couple years have very low read noise.  So it makes sense that sensors of the same size have similar performance at high ISO.  I’ve compared ISO 3200 images from the D90 and D7000 and they pretty much look the same.  The D90 actually has lower read noise than the D7000 at ISOs 1600-6400, which is why its DR matches or surpasses the D7000 at those sensitivities.

I’ll bet that you don’t own a recent Nikon.  From a dark area such as your crop, a Nikon owner would expect to be able to bring out that much detail.  The D7000’s DR boost comes from having a higher pixel saturation point, as well as lower read noise at low ISO.  To see the expanded DR in action you need a scene with a large DR, such as an indoor shot of a window on a sunny day.


I have a D700. Does that count as a recent Nikon? How much did you bet?

Whatever the technical reasons that might explain why a pixel on one particular sensor can 'suck up' more light (as you put it) than a larger pixel on another sensor, the fact remains, according to DXO, that the smaller D7000 pixel appears to have a higher DR than the larger D700 pixel, at base ISO. The fact that it doesn't have a higher DR than the D700 at high ISOs would seem to me to be a matter of the sophistication and power of in-camera processors and analog-gain transistors.

As I understand, a digital camera has only one 'real' ISO, known as the base ISO. All higher ISOs than base are, in reality, underexposures that are subject to analog gain prior to A/D conversion, and further processing along the chain before the data is written to the memory card.

Now I agree that the scene I've shown may not necessarily be ideal for the purposes of demonstrating the DR potential of the D7000, but it was the best I could get after trawling the internet. A RAW image would be ideal.

If you have a better image demonstrating the DR capability of the D7000, please show it.

Title: Re: Nikon D7000 Dynamic Range
Post by: Graystar on November 11, 2010, 09:28:46 am
I have a D700. Does that count as a recent Nikon?

Sure.  Your D700 will pull up detail like that better than the D7000. 

Whatever the technical reasons that might explain why a pixel on one particular sensor can 'suck up' more light (as you put it) than a larger pixel on another sensor, the fact remains, according to DXO, that the smaller D7000 pixel appears to have a higher DR than the larger D700 pixel, at base ISO. The fact that it doesn't have a higher DR than the D700 at high ISOs would seem to me to be a matter of the sophistication and power of in-camera processors and analog-gain transistors.

It has to do with read noise.  At ISO 200 the read noise on the D700 is high.  At higher ISO levels the read noise drops by more than half.  The D7000 has a read noise level that starts low and stays low.  And it's more efficient as well.

The D7000 is a great camera with a very efficient sensor.  I’d still rather have a D700...though.

If you have a better image demonstrating the DR capability of the D7000, please show it.

I haven’t look extensively for one...I’m sure there must be some better images somewhere, but I found this over at DPReview...
http://forums.dpreview.com/forums/read.asp?forum=1034&message=36843187


Title: Re: Nikon D7000 Dynamic Range
Post by: RFPhotography on November 11, 2010, 10:10:25 am
Bloody hell.  My head hurts. 
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 11, 2010, 10:16:43 am
Sure.  Your D700 will pull up detail like that better than the D7000.  

It has to do with read noise.  At ISO 200 the read noise on the D700 is high.  At higher ISO levels the read noise drops by more than half.  The D7000 has a read noise level that starts low and stays low.  And it's more efficient as well.

The D7000 is a great camera with a very efficient sensor.  I’d still rather have a D700...though.

I haven’t look extensively for one...I’m sure there must be some better images somewhere, but I found this over at DPReview...
http://forums.dpreview.com/forums/read.asp?forum=1034&message=36843187


Of course it has to do with read noise, as well as may other factors, but that doesn't explain why one pixel has significantly lower read noise, as a proportion of total signal, than another pixel, like a D700 pixel which is larger. It's not the absolute size of the read noise that's important, but it's relative size compared with the strength of the signal.

The landscape shot at dpreview is a nice shot, clear and sharp, but it doesn't demonstrate the limits of the D7000 dynamic range. In order to do that you need a subject with a very high brightness range which not only includes bright clouds but dense shadows in the undergrowth, not just normal shade. I get a sense that any camera could have taken that shot at dpreview, including the first DSLR I ever bought, the 6mp Canon D60 about 7 years ago.

You know, were not talking about a miniscule, pixel-peeping DR difference here, at base ISO, like 1/4th or 1/3rd of a stop, but a whacking 1 & 1/2 stops.

The D700 has a lower pixel count than the D7000, so there's no downsizing advantage for the D700 regarding noise and DR, but there is for the D7000.

At normalised print sizes, the largest size you would make a D700 print without interpolation, the D7000 has a 1 & 2/3rd stop DR advantage. That really is significant. If I had a D7000, I'd demonstrate it, or prove DXO wrong.


Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on November 11, 2010, 10:51:10 pm
Ray,

Just for your information, Phase One has a couple of comparable images for download, which I may consider good for comparison. The download link is here:

http://www.phaseone.com/en/Downloads/Sample-images.aspx


These images are in some Capture One format, so you need Capture One to read them. I downloaded Capture One demo, and exported the files as DNGs so I could process them in Lightroom. Phase One had three images, Architecture/Landscape low ISO, outdoor portrait and high ISO indoor portrait. In my view the outdoor portrait comparison was essentially worthless, but the other two pretty good. The comparison on the Architecture/Landscape image was shot on Canon 1DIIIs the others on Nikon D3.

That P65+ architecture image was incredibly good, having much better DR than the Canon image, AT THE PIXEL LEVEL.

Preprocessing the images in Capture One may give the P65+ an unfair advantage, but may have been necessary.

My article on these images is here: http://echophoto.dnsalias.net/ekr/index.php/photoarticles/41-phase-one-images-for-download

I didn't show the images, because I did not ask Phase One to permit publication of their images.

Best regards
Erik



Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on November 11, 2010, 11:23:25 pm
Hi,

A generic comment on DR. I really think that the discussion around DR is overblown. Much of the discussion at all is overblown.

My experience is that DR is essentially plentiful when shooting with present days DSLRs at base ISO correctly exposing to the right. In real life we always have lens flare that reduces the achievable DR anyway. If we shoot in a dark cathedral and want to reproduce shadow detail and window mosaics at the same time we may need to use HDR (combining a bracketed exposure in a single image) or similar techniques. But, in my experience a correctly HTTR exposed image is as good as HDR in most cases.

One issue that is overlooked is MTF. MTF measures how much contrast an optical system can transfer for a certain feature size. The feature size is described as cycles, lp/mm, frequency etc. Anyway, MTF diminishes as feature size is reduced.  In an MTF versus frequency plot the MTF value drops almost exactly linearly for a diffraction limited (that is perfect) lens at a given aperture.

Therefore, doubling image size would also double the contrast transferred for a certain size of feature. A larger format would reproduce an object larger on sensor would the angle of view kept constant. So significantly more detail would be visible in the darks, simply because shadow detail would have more contrast.

The reasoning above is of course based on the assumption that MTF vs. resolution is similar on both systems. This may or may no be the case. Ray used to argue that larger formats need to be stopped down more than smaller format to keep DOF constant. This is indeed true, but maximum DOF is not always desirable. MF lenses used to have lower MTF at given lp/mm than 135, but we have a new generation of MF lenses like some of the Phase One lenses and the new Leica lenses for the S2 system that are brilliant performers, and so are the new Schneider and Rodenstock digital lenses. IF YOU GET A DECENT COPY!

http://www.josephholmes.com/news-medformatprecision.html (why not read this?! ;-)

My opinion is that we don't need to argue about things that we don't have tested. I would suggest that we learn to use what we have optimally. It may be that we perceive a need for better quality, and MF-digital may the way to achieve it. That's fine.

But while discuss the fine point before setting up the camera on a decent tripod, use mirror lockup and a cable release (or self timer) or testing and adjusting auto focus?

Best regards
Erik







Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 12, 2010, 12:56:35 am
Hi,

A generic comment on DR. I really think that the discussion around DR is overblown. Much of the discussion at all is overblown.

My experience is that DR is essentially plentiful when shooting with present days DSLRs at base ISO correctly exposing to the right. In real life we always have lens flare that reduces the achievable DR anyway. If we shoot in a dark cathedral and want to reproduce shadow detail and window mosaics at the same time we may need to use HDR (combining a bracketed exposure in a single image) or similar techniques. But, in my experience a correctly HTTR exposed image is as good as HDR in most cases.

One issue that is overlooked is MTF. MTF measures how much contrast an optical system can transfer for a certain feature size. The feature size is described as cycles, lp/mm, frequency etc. Anyway, MTF diminishes as feature size is reduced.  In an MTF versus frequency plot the MTF value drops almost exactly linearly for a diffraction limited (that is perfect) lens at a given aperture.

Therefore, doubling image size would also double the contrast transferred for a certain size of feature. A larger format would reproduce an object larger on sensor would the angle of view kept constant. So significantly more detail would be visible in the darks, simply because shadow detail would have more contrast.

The reasoning above is of course based on the assumption that MTF vs. resolution is similar on both systems. This may or may no be the case. Ray used to argue that larger formats need to be stopped down more than smaller format to keep DOF constant. This is indeed true, but maximum DOF is not always desirable. MF lenses used to have lower MTF at given lp/mm than 135, but we have a new generation of MF lenses like some of the Phase One lenses and the new Leica lenses for the S2 system that are brilliant performers, and so are the new Schneider and Rodenstock digital lenses. IF YOU GET A DECENT COPY!

http://www.josephholmes.com/news-medformatprecision.html (why not read this?! ;-)

My opinion is that we don't need to argue about things that we don't have tested. I would suggest that we learn to use what we have optimally. It may be that we perceive a need for better quality, and MF-digital may the way to achieve it. That's fine.

But while discuss the fine point before setting up the camera on a decent tripod, use mirror lockup and a cable release (or self timer) or testing and adjusting auto focus?

Best regards
Erik


Thanks Erik. I did see that link to the Phase comparison images before, and attempted to download them and have a look. But something went wrong, or I did something wrong and my trial version of C1 didn't seem to recognise the files. It became un unnecessary hassle, so I gave up.

The fact is, I don't need to be convinced that P65+ images, at base ISO, are better in all respects than Canon 1Ds3 images, including DR. The DXO results indicate that this is so. I've no reason to disbelieve them.

What amazes me is how Nikon have overtaken Canon with regard to these image quality parameters, particularly DR.

If you want the best low light performance, get the D3s. If you want the best DR performance at base ISO get the D3X or the D7000.

It's truly remarkable that this cropped-format D7000 has the DR performance of the D3x all the way from ISO 100 to ISO 6400. At every ISO they are about the same. The differences are negligible.

However, they are not the same for all of the other parameters, such as SNR and color sensitivity. The D3X is slightly better than the D7000 at each ISO setting, although one might wonder how significant such differences are in practice. For example, DXOMark comment that a difference of one bit in color sensitivity is barely noticeable. The differences in color sensitivity between the D3X and D7000, at all ISOs, is in the order of 1.1 to 1.3 bits, according to the graphs.

Of course, the differences in total sensor resolution are significant. An increase of 50% in pixel count is not to be sneezed at, and as you've pointed out before, the larger format can often access the same image detail from the lens at a higher MTF and a lower lpp/mm.

For those who are always searching for the shallowest of DoF, the larger format has an advatage. A lens at F2.8 will tend to produce sharper images on FX than the same quality of lens at F2.8 on the DX format, as well as producing a shallower DoF.

If the DoF is equalized, FX format at F4.5 (for example) will also usually be sharper than DX at F2.8, but may not be sharper at F9 than DX at F5.6.

What might be interesting to consider is what happens if we need to equalize both DoF and shutter speed (because the subject is moving). We might then be comparing say a D700 at F9 and ISO 400, with a D7000 at F5.6 and ISO 160.

In this situation, the DXO graphs are telling me that the D7000 should produce approximately a full stop better DR than the D700 at all ISOs that differ by this 'DoF/ISO/shutter speed' factor of approximately 1 & 1/3rd stops.

Furthermore, the FX D700 in this situation, loses all advantages with regard to SNR, tonal range and color sensitivity. It's slightly worse in fact, but let's not quibble.

Do you agree with this analysis?

Cheers!
Title: Re: Nikon D7000 Dynamic Range
Post by: stamper on November 12, 2010, 03:24:44 am
Quote

Furthermore, the FX D700 in this situation, loses all advantages with regard to SNR, tonal range and color sensitivity. It's slightly worse in fact, but let's not quibble.

Unquote

Ray that is why you started the thread ..... to quibble! You could start a fight in an empty house. Bet you are happy to have two more to shadow box with? :) ;) ;D
Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on November 12, 2010, 03:05:40 pm
Hi,

I have both DX and FX, Sony Alpha 700 and Sony Alpha 900, in my case. The feeling I have is that I have a tendency to take advantage of what I have. The Alpha 700 with it's 16-80/3.5-4.5 lens is more nimble and definitively good enough, most of the time. With the Alpha 900 I want to go for perfection. It's like shooting MF film and 135 Film. When shooting MF I used to adjust to MF, very little DOF, camera on tripod and so on. If I was shooting MF the 135 way the pictures were like 135.

A2 prints from the Alpha 700 can be impressive. I got the response at the photo club: Ah, one of your stitched full frames?! No, just a cropped APS-C!

The technique we have now is just incredibly good!

Best regards
Erik

Thanks Erik. I did see that link to the Phase comparison images before, and attempted to download them and have a look. But something went wrong, or I did something wrong and my trial version of C1 didn't seem to recognise the files. It became un unnecessary hassle, so I gave up.

The fact is, I don't need to be convinced that P65+ images, at base ISO, are better in all respects than Canon 1Ds3 images, including DR. The DXO results indicate that this is so. I've no reason to disbelieve them.

What amazes me is how Nikon have overtaken Canon with regard to these image quality parameters, particularly DR.

If you want the best low light performance, get the D3s. If you want the best DR performance at base ISO get the D3X or the D7000.

It's truly remarkable that this cropped-format D7000 has the DR performance of the D3x all the way from ISO 100 to ISO 6400. At every ISO they are about the same. The differences are negligible.

However, they are not the same for all of the other parameters, such as SNR and color sensitivity. The D3X is slightly better than the D7000 at each ISO setting, although one might wonder how significant such differences are in practice. For example, DXOMark comment that a difference of one bit in color sensitivity is barely noticeable. The differences in color sensitivity between the D3X and D7000, at all ISOs, is in the order of 1.1 to 1.3 bits, according to the graphs.

Of course, the differences in total sensor resolution are significant. An increase of 50% in pixel count is not to be sneezed at, and as you've pointed out before, the larger format can often access the same image detail from the lens at a higher MTF and a lower lpp/mm.

For those who are always searching for the shallowest of DoF, the larger format has an advatage. A lens at F2.8 will tend to produce sharper images on FX than the same quality of lens at F2.8 on the DX format, as well as producing a shallower DoF.

If the DoF is equalized, FX format at F4.5 (for example) will also usually be sharper than DX at F2.8, but may not be sharper at F9 than DX at F5.6.

What might be interesting to consider is what happens if we need to equalize both DoF and shutter speed (because the subject is moving). We might then be comparing say a D700 at F9 and ISO 400, with a D7000 at F5.6 and ISO 160.

In this situation, the DXO graphs are telling me that the D7000 should produce approximately a full stop better DR than the D700 at all ISOs that differ by this 'DoF/ISO/shutter speed' factor of approximately 1 & 1/3rd stops.

Furthermore, the FX D700 in this situation, loses all advantages with regard to SNR, tonal range and color sensitivity. It's slightly worse in fact, but let's not quibble.

Do you agree with this analysis?

Cheers!

Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 12, 2010, 06:05:57 pm
Hi,

I have both DX and FX, Sony Alpha 700 and Sony Alpha 900, in my case. The feeling I have is that I have a tendency to take advantage of what I have. The Alpha 700 with it's 16-80/3.5-4.5 lens is more nimble and definitively good enough, most of the time. With the Alpha 900 I want to go for perfection. It's like shooting MF film and 135 Film. When shooting MF I used to adjust to MF, very little DOF, camera on tripod and so on. If I was shooting MF the 135 way the pictures were like 135.

A2 prints from the Alpha 700 can be impressive. I got the response at the photo club: Ah, one of your stitched full frames?! No, just a cropped APS-C!

The technique we have now is just incredibly good!

Best regards
Erik



Erik,
I know what you mean. When I got my first full frame DSLR, the Canon 5D about 5 years ago, I was very pleased with that extra image quality that resulted from a better SNR, smoother tonal range and better color sensitivity. It was certainly very apparent when processing images and examining detail at 100% on the monitor, but I can't say that I spent much time comparing large prints of identical scenes taken with the 5D and other cropped formats, even when I later acquired a APS-C format with higher pixel count than the 5D, the 15mp 50D.

But I do remember quite vividly, when I took the first shots with my 5D, being very disturbed by the noise and banding in the deep shadows when, for example, shooting the scene through the window of my living room, exposing for the bright clouds outside.

In fact, I immediately returned the camera and tried another copy from a different series of serial numbers, implying the camera was from a different batch.

It was slightly better regarding banding, so I kept it. Now I understand if a professional photographer were assigned the task of photographing someone's living room whilst simultaneously showing off the view through the window, he might bring in some heavy lighting equipment so the interior were correctly exposed without the black shadows one tends to get when using a single flash source. Or he might even go to the the trouble of sticking a gel over the windows to act like a neutral density filter, if he were paid enough.

But I'm just an amateur, and I prefer the easier option if one is available. If I find myself in the position of wanting to photograph the interior of the humble abode of a Nepalese farmer and his family, at an altitude of 3,000 metres against a magnificant backdrop of the Himalayas, I'd like to prepare myself with a camera capable of the job.

In such circumstances, the 5D without appropriate internal lighting, would display severe and unacceptable shadow noise. The D7000 probably wouldn't.

Checking the DXOMark graphs again, I see that at ISO 100, the D7000 has 2 & 2/3rds stops greater DR than the 5D (or 2.74 stops to be precise).  Even Stamper would agree that's one enormous nit.

To put this in perspective, the Canon 5D has only 1.1 stops higher DR, at base ISO, than the P&S Canon G10. Does that seem incredible? May I suggest not, if you consider the other parameters, such as tonal range and color sensitivity. There, the Canon 5D is streets ahead of the G10, as well as regards SNR at 18% grey.

But it's not ahead of the D7000. SNR, tonal range, color sensitivity on the D7000 are at least as good as those of the 5D, sometimes slightly better, sometimes slightly worse depending on ISO.

Since the D7000 has a higher pixel count than the 5D, I would not expect any resolution advantage from the 5D, except at very wide apertures.
Title: Re: Nikon D7000 Dynamic Range
Post by: RFPhotography on November 13, 2010, 07:53:58 am
HEADLINE:  Technology improves!

Shock of shocks.  Now go out and take some pictures.
Title: Re: Nikon D7000 Dynamic Range
Post by: bjanes on November 13, 2010, 09:59:23 am
We probably all know by now that the DR of the D7000 at base ISO (together with that of the Pentax K-5) trumps every other digital camera on the market, whatever the format.

The P65+ is a laggard and under-achiever compared to the tiny format D7000, as regards DR.

But before you go purple in the face with rising blood pressure, and release yourself into an explosion of expletives directed against DXO, let's consider for a moment what the DXOMark rankings really mean.

The best discussion of the DXO DR ratings that I know of is the thread started by Emil Martinec (http://www.luminous-landscape.com/forum/index.php?topic=42158.0). The DXO DR is closely related to the engineering definition of DR. DXO DR uses a SNR of 1 in the denominator, whereas the engineering definition uses the read noise in the denominator, which is essentially the noise at zero exposure (for cameras like the Canons which use an exposure offset and do not clip the signal).

The D7000 has a very high DR according to the DXO criterion, because it has low read noise. However, noise over most of the useful photographic range is determined by shot noise, and larger sensor sizes will have a better SNR over this useful range. A SNR of 1 is not acceptable for most photographic purposes. Full frame 35 mm has double the sensor size of the cropped frame D7000 and the P65+ has twice the sensor area over a full frame 35 mm dSLR.

Regards,

Bill
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 13, 2010, 12:17:36 pm
The best discussion of the DXO DR ratings that I know of is the thread started by Emil Martinec (http://www.luminous-landscape.com/forum/index.php?topic=42158.0). The DXO DR is closely related to the engineering definition of DR. DXO DR uses a SNR of 1 in the denominator, whereas the engineering definition uses the read noise in the denominator, which is essentially the noise at zero exposure (for cameras like the Canons which use an exposure offset and do not clip the signal).

The D7000 has a very high DR according to the DXO criterion, because it has low read noise. However, noise over most of the useful photographic range is determined by shot noise, and larger sensor sizes will have a better SNR over this useful range. A SNR of 1 is not acceptable for most photographic purposes. Full frame 35 mm has double the sensor size of the cropped frame D7000 and the P65+ has twice the sensor area over a full frame 35 mm dSLR.

Regards,

Bill


It looks as though I read that thread, Bill, because I contributed a post on page 3, but thanks for the link.

The issue of whether the full range of DR as described by DXO can be used for acceptable photographic results seems a separate issue to me. I've always been willing to accept that the photographic detail in those last couple of stops, detail that one might try to bring out by raising the shadows in an image of a scene with a high brightness range, is likely to be of unacceptable quality for artistic purposes, but possibly still useful for certain other purposes, such as identifying a car number plate in a photo taken at night.

For me, the issue is one of relativity. If the D7000 is described as having 2.74 stops higher DR than the 5D (Mk1), does that mean that at base ISO I could expect similar quality in the shadows from a D7000 image which had been underexposed 2 & 2/3rds stops, to what I would get from an ETTR exposure on the 5D, in the same shadows?

I understand the principle that a sensor which is double the area of another sensor will be exposed to double the amount of light when taking the the same scene at the same T-stop and shutter speed. But what happens to that light after it has reached the sensor is another matter. Some sensors have a higher quantum efficiency, for example, or more sophisticated methods of processing the analog signal, or voltage.

If there's a case to be made that photon shot noise, and/or normal lens flare will nullify those extra stops of DR that DXOMark claim the D7000 has, then I'd like to see the evidence.

I don't want to buy a D7000 largely on the basis it has terrific DR, only to find out later that in practice it has no greater DR than the Canon 60D as a result of factors which DXOMark did not take into consideration.

So far, the results of every test on my own equipment I've made, corresponds very closely with DXOMark's results.

I'm reminded of a test I carried out in Chiang Mai a few years ago. I rented an apartment for a couple of months and had free (or cheap) broadband access. The subjective nature of DR came up on an LL thread, and Jonathan Wienke devised a DR test chart containing various sizes of letters and numbers which, as a result of some discussion amongst us, would distinguish between acceptable quality of DR and the absolute limits, limits which would presumably be similar to the engineering definition of DR.

I downloaded Jonathan's image, printed it out on my base-model Epson printer (cheap as chips in Thailand), and proceeded to photograph the chart in constant lighting, starting with an ETTR, then reducing exposure by one stop with each shot.

I took more than 12 shots. On examining the images, I found there was still some detail to be observed in the 11th shot. The largest letters or numerals were still legible, but only just.

Of course, an argument then ensued, mainly between Jonathan, myself and John Sheehey, as I recall, as to whether or not that barely legible detail in the 11th stop deserved to be part of the specified dynamic range of the 5D.

I'm now rather surprised to see in the DXOMark graphs that the Canon 5D has a DR at base ISO of 11.13 EV. Close enough!

Cheers!
Title: Re: Nikon D7000 Dynamic Range
Post by: RFPhotography on November 13, 2010, 01:00:58 pm
OK, let me see if I can get this straight.

You're in a terrific setting like Thailand and you're wasting time farting around with dynamic range tests and screwing around on the internet?   ???

This is exactly why the LL fora are known as the place for the measurebators to hang out.   ::)

Title: Re: Nikon D7000 Dynamic Range
Post by: kers on November 13, 2010, 08:20:48 pm
It is interesting to see how digital photography gets better and better. I just used a Nikon d3s and was amazed how much colour it sees in almost total darkness using a 1.4 lens wide open.
My eyes are less sensitive! and see for sure less colour.
( and i am not blind at all)
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 13, 2010, 08:26:27 pm
OK, let me see if I can get this straight.

You're in a terrific setting like Thailand and you're wasting time farting around with dynamic range tests and screwing around on the internet?   ???

This is exactly why the LL fora are known as the place for the measurebators to hang out.   ::)


Not only farting around with dynamic range tests, but farting around reading books, and farting around photographing temples at night with only street lighting for illumination, and being concerned about unacceptable noise in the shadows; and farting around getting to know the limitations of my equipment, sometimes processing images in the evening on my laptop to see how the day's shooting went and to see what mistakes I made, in the hope of not repeating them.

A holiday which allows for no time to fart around is no holiday in my opinion. My last trip was an organised cruise along rivers in Europe and Russia. Everyday there were organised tours from morning till dusk, then yet more tours in the evenings to see shows, Russian folk dancing, ballets, concerts etc. By the time I got back to Australia, I felt so exhausted I needed a holiday.

Get my point?
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 13, 2010, 08:56:22 pm
It is interesting to see how digital photography gets better and better. I just used a Nikon d3s and was amazed how much colour it sees in almost total darkness using a 1.4 lens wide open.
My eyes are less sensitive! and see for sure less colour.
( and i am not blind at all)

Indeed! I find the low-light capability of modern cameras very useful. Taking photos in low light situations using a Speedlite or built-in flash can produce unwanted results such as black shadows around edges, and total darkness prevailing just a few metres away because of the limited range of the flash.

Flash can also be annoying for the subject and can bring unwanted attention to oneself. Some time ago whilst photographing a cabaret show in Bangkok, whilst sat in the first row, the manager approached me and asked me to stop using flash because it was distracting the performers. Of course I complied and for the rest of the show had my 5D set on ISO 1600 & 3200. Frequently the DoF was not sufficient or the shutter speed too slow for a sharp shot consistent with reasonably acceptable noise.

In that situation, a D3s would have been ideal, but that camera's a bit too heavy and expensive for me. A D7000 would not have helped much in that situation, except in respect of a more extensive DoF at the same aperture and shutter speed.

Title: Re: Nikon D7000 Dynamic Range
Post by: stamper on November 14, 2010, 04:21:31 am
Ray .... the men in white coats are coming. Don't resist them, they only want to help. :) ;) 8)
Title: Re: Nikon D7000 Dynamic Range
Post by: BernardLanguillier on November 14, 2010, 05:27:21 pm
The key thing I will retain from these discussions isn't so much how good the D7000 is or it not relative to the P65+. It is also not how close the DxO DR is to real DR.

What I retain, especially after reading fascinating threads at DPreview, is that most people - including people going pretty deep into the technicalities of photography - are not able to measure DR as part of their photographic experience. DR is most often confused with the ability to recover highlights (a property that only depends on sensor ISO calibration) while it is only about noise in under-exposed areas.

Designing a sensor that will have very clean shadows involve making other compromises in order to achieve a general balance. This involves huge R&D investments and is probably an order of magnitude more complex than raising pixel count. Yet most customers don't see it and keep fighting every objective measure of it.

We - more or less advanced photographers - have been just as guilty as the rest. We have been saying "more DR", but are mostly unable to recognize it when it shows up. :)

The net result of this is most probably going to be next generation sensors with less DR... why should these companies keep investing huge money to improve a camera characteristic that we think we care about, but actually don't?

They would all be much better off do what Phaseone does, under-expose all their shots one stop by turning ISO 100 into ISO 200, and calibrate the software chain so as to be able to recover one stop of highlights. So much so for the myth that advanced photographers prefer to shoot with slides films.  ;D

Cheers,
Bernard
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 14, 2010, 09:25:16 pm
The key thing I will retain from these discussions isn't so much how good the D7000 is or it not relative to the P65+. It is also not how close the DxO DR is to real DR.

What I retain, especially after reading fascinating threads at DPreview, is that most people - including people going pretty deep into the technicalities of photography - are not able to measure DR as part of their photographic experience. DR is most often confused with the ability to recover highlights (a property that only depends on sensor ISO calibration) while it is only about noise in under-exposed areas.

Designing a sensor that will have very clean shadows involve making other compromises in order to achieve a general balance. This involves huge R&D investments and is probably an order of magnitude more complex than raising pixel count. Yet most customers don't see it and keep fighting every objective measure of it.

We - more or less advanced photographers - have been just as guilty as the rest. We have been saying "more DR", but are mostly unable to recognize it when it shows up. :)

The net result of this is most probably going to be next generation sensors with less DR... why should these companies keep investing huge money to improve a camera characteristic that we think we care about, but actually don't?

They would all be much better off do what Phaseone does, under-expose all their shots one stop by turning ISO 100 into ISO 200, and calibrate the software chain so as to be able to recover one stop of highlights. So much so for the myth that advanced photographers prefer to shoot with slides films.  ;D

Cheers,
Bernard


Those are a good points, Bernard.

Speaking for myself, the only reason I'm concerned about issues of DR, is because in the past I've sometimes been disappointed with the quality of shadow detail, not only regarding shadow detail in certain slides I've scanned, but also the shadow detail at base ISO from DSLRs I've used.

In the house of a friend of mine, there's a very large and impressive print of a waterfall hanging on the wall, taken by a professional photographer who appears to have done all the right things, neutral density filter for a slow shutter speed, and polariser to smooth the specral reflections on the water surface at the foot of the falls.

But in my view, the scene has one major flaw. All the deep shadows are totally black (0,0,0,).

From a distance, that's not too bad, but from close-up it looks a bit odd to me, a bit unnatural.

Would it be fair to presume that the reasons such shadows are totally black is not just for an esthetic reason, black is beautiful, but to hide the fact that the detail in those shadows is crap, due to a lack of sufficient DR capability of the camera and the processing chain?

Reluctant as I am to show my rejects in order to demonstrate a point, here are a couple of casual shots of a waterfall in a rainforest taken several years ago with a 6mp DSLR and Sigma zoom at base ISO. They were casual, no tripod or ND filter, but correctly exposed in accordance with the principles of ETTR. The 100% crops highlight the problems in the deep shadows.

Another interesting characteristic of the D7000, which has been noticed by some perceptive posters at dpreview, is that DR is now so good at base ISO, there is no image-quality advantage in using a high ISO setting.

In other words, the D7000 now behaves like a DB. An ISO 800 shot is no better than an ISO 100 shot underexposed 3 stops.

There are both advantages and disadvantages to this situation, ie, underexposing at base ISO instead of increasing ISO for the desired shutter speed at the desired aperture.

The disadvantage is that the review jpeg on the camera's LCD might be too dark for you to properly assess if you've captured the moment successfully, although I tend to think this is a trivial concern. If you havn't captured the moment successfully, too bad. The moment has passed.

For me, I think the main purpose of the LCD review is to determine whether I've blown the highlights, which brings me to the advantages of this characteristic of the D7000.

The concept of ETTR (expose to the right) has been a much-discussed topic on this forum over the years. So much so that the issues should now be clear to everyone.

If you do not give a 'full' exposure, whatever the ISO setting, you are not going to get the full qualities of tonal range and low noise that your camera is capable of.

However, there's a huge practical problem with this methodology of ETTR. In one's attempt to get a 'full' exposure, it's just too easy to blow highlights.

If you have the time, and can retake the shot because the 'moment' is not critical, the LCD review image is useful, at base ISO, even on the D7000.

However, if you are not as base ISO because you need a faster shutter speed and/or need to stop down for greater DoF, then the risk of blowing highlights is of greater concern.

This quality of the D7000 seems to me to be a significant advantage for 'manual' shooters. You choose the aperture and shutter speed that's required for the shot, in the circumstances, whatever the lighting. If you raise ISO, you have to worry about ETTR issues. If you leave the camera at base ISO, the image will be underexposed, but you can be completely confident there will be no blown highlights and no loss of image quality, when shooting RAW of course, after compensating for the underexposure in ACR.

I like it.

Title: Re: Nikon D7000 Dynamic Range
Post by: BernardLanguillier on November 14, 2010, 10:21:11 pm
Speaking for myself, the only reason I'm concerned about issues of DR, is because in the past I've sometimes been disappointed with the quality of shadow detail, not only regarding shadow detail in certain slides I've scanned, but also the shadow detail at base ISO from DSLRs I've used.

We have been screaming for more DR, but my point is that we are not always being super coherent on this one. The logical consequence should be less focus on DR from our camera manufacturers. As always there is strong inertia between consumer demand and product development so I believe that next gen products - speced one or 2 years ago - will still show an improvement, but my guess is that the following generation will see either a stagnation or a decrease of DR since few people really care. :)

You'd think that all landscape, architecture, product,... photographers would have the same concerns, but this doesn't appear to be the case, or at least to be enough the case to translate into significantly added sales for those companies having invested huge amounts of money in really improving DR:

- Some photographers really don't care, they focus on the same scenes they have been focusing on since slides days and just ignore the other scenes. You don't need DR then and they might be right, what is nicer than a well exposed slide with sweet light hitting the very right spot in a composition?
- Some do care and are using these cameras/backs delivering more real world DR,
- Some do care but they don't know that there is something better than their existing camera in terms of shadow noise,
- Some do care, know there is something better than their existing camera but don't see the value proposition of DR as being good enough to overcome the cost of a switch now (heck, other brands will catch up some day),
- Some do care, know there is something better than their existing camera but won't admit it because of some crazy self defeating fanboy behavior or whatever even less admissible reasons,
- ...

I am NOT thinking of any person in particular.

Cheers,
Bernard
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 15, 2010, 12:52:54 am
We have been screaming for more DR, but my point is that we are not always being super coherent on this one. The logical consequence should be less focus on DR from our camera manufacturers. As always there is strong inertia between consumer demand and product development so I believe that next gen products - speced one or 2 years ago - will still show an improvement, but my guess is that the following generation will see either a stagnation or a decrease of DR since few people really care. :)

Not sure about that, Bernard. What we seem to have now are, on the one hand, cameras that have brilliant DR at low ISO, such as the D3X and D7000, but modestly good DR at high ISO, and on the other hand, cameras that have brilliant DR at high ISO, such as the D3s, but only modestly good DR at low ISO.

Hopefully, DSLRs of the future, whether Nikon or Canon, will combine these two strengths so we will have the best of both worlds.  ;D
Title: Re: Nikon D7000 Dynamic Range
Post by: BernardLanguillier on November 15, 2010, 01:19:53 am
Not sure about that, Bernard. What we seem to have now are, on the one hand, cameras that have brilliant DR at low ISO, such as the D3X and D7000, but modestly good DR at high ISO, and on the other hand, cameras that have brilliant DR at high ISO, such as the D3s, but only modestly good DR at low ISO.

Hopefully, DSLRs of the future, whether Nikon or Canon, will combine these two strengths so we will have the best of both worlds.  ;D

That will only happen if they feel their customers care and it helps selling more cameras at a higher price point.

Cheers,
Bernard
Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on November 15, 2010, 01:32:53 am
Hi!

Whats your main wish? Better DR or usable histograms?

There are two ways to increase DR, one is to increase full well capacity, the other is to reduce read noise. The second option improves DxO ratings but may have little effect in normal photography which is dominated by shot noise, at least in my humble opinion.

Usable histograms would help us to really expose to the right and improve photon statistics.

The look of the noise also matters, some noise is worse than others.

Best regards
Erik



That will only happen if they feel their customers care and it helps selling more cameras at a higher price point.

Cheers,
Bernard

Title: Re: Nikon D7000 Dynamic Range
Post by: RFPhotography on November 15, 2010, 07:38:11 am
Not only farting around with dynamic range tests, but farting around reading books, and farting around photographing temples at night with only street lighting for illumination, and being concerned about unacceptable noise in the shadows; and farting around getting to know the limitations of my equipment, sometimes processing images in the evening on my laptop to see how the day's shooting went and to see what mistakes I made, in the hope of not repeating them.

A holiday which allows for no time to fart around is no holiday in my opinion. My last trip was an organised cruise along rivers in Europe and Russia. Everyday there were organised tours from morning till dusk, then yet more tours in the evenings to see shows, Russian folk dancing, ballets, concerts etc. By the time I got back to Australia, I felt so exhausted I needed a holiday.

Get my point?

I do get your point.  It seems you're missing mine; however.  As an aside, organised tours aren't my cup of tea either.  I prefer to find and explore on my own.

Erik summed it up quite nicely in his last comment.  Of course I want to understand the limits of my equipment (and I do) but I'm not going to waste time replicating DxO or DPReview or anybody else's tests to try and do it.  And I'm certainly not going to set out to try to prove DxO or other test sights wrong.  And most certainly not going to do it while on vacation.  My interests in the limitations of my gear are around practical uses.  Like many, I'll research new gear by looking at what I feel are credible reviews but those only form part of the buying decision and a minority part at that.  The larger part of the decision making process will come from the real world experiences of people whose opinions I value and my own experience from renting/borrowing before buying or taking a memory card to the store and firing of a bunch of shots in different conditions in store and bringing those back to my office to evaluate.  I've actually been asked to leave a store because the salesperson felt I was taking too many shots with their demo camera.  Apparently he worked on the look but don't touch theory of selling.  ::) 

I also understand that, as I noted earlier, technology improves.  It's not a shock when new equipment is better than previous generation equipment.  It is a disappointment when new is not as good as prior.  It's also a serious disappointment; and a larger one than with respect to the technological aspects, when serious design, firmware programming and manufacturing QC problems plague a manufacturer.  If a camera fails in the field it doesn't matter how good its DR is.  If you can't focus a camera in the field, it doesn't matter how good its DR is.  If a camera's mirror falls off in the field it doesn't matter how good its DR is.

So, in conclusion, I'm far more concerned with the practical aspects of what a camera is capable of than the theoretical. 
Title: Re: Nikon D7000 Dynamic Range
Post by: bjanes on November 15, 2010, 08:37:45 am

The concept of ETTR (expose to the right) has been a much-discussed topic on this forum over the years. So much so that the issues should now be clear to everyone.

If you do not give a 'full' exposure, whatever the ISO setting, you are not going to get the full qualities of tonal range and low noise that your camera is capable of.

However, there's a huge practical problem with this methodology of ETTR. In one's attempt to get a 'full' exposure, it's just too easy to blow highlights.

If you have the time, and can retake the shot because the 'moment' is not critical, the LCD review image is useful, at base ISO, even on the D7000.

However, if you are not as base ISO because you need a faster shutter speed and/or need to stop down for greater DoF, then the risk of blowing highlights is of greater concern.

This quality of the D7000 seems to me to be a significant advantage for 'manual' shooters. You choose the aperture and shutter speed that's required for the shot, in the circumstances, whatever the lighting. If you raise ISO, you have to worry about ETTR issues. If you leave the camera at base ISO, the image will be underexposed, but you can be completely confident there will be no blown highlights and no loss of image quality, when shooting RAW of course, after compensating for the underexposure in ACR.


Ray,

Excellent points. By extension of your thoughts, I propose that exposure to the right (ETTR) really applies only to base ISO. If you expose at base ISO so that the highlights are just short of clipping and then double the camera ISO, the sensor will only be at half saturation (full well), but the electronic gain will be increased so that the histogram is moved to the right and you have a nice looking histogram. However, the shot noise will be the same as with the histogram of the "underexposed" shot at base ISO.

With the old generation of cameras such as the D3 and D3s, the increase in ISO reduced read noise and improved the SNR in the shadows. However, with the newer generation cameras with improved electronics and ADCs, read noise is optimal at base ISO and the use of a higher ISO results in less headroom for the highlights and can result in burnt highlights. Even with older cameras, one can increase ISO only to the point where read noise approaches a minimum (easily predicted by the DXO DR curves as Emil explains in the above quoted link. For the Nikon D3, this occurs at about ISO 600 where the DR curve becomes linear.

Regards,

Bill
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 15, 2010, 10:45:19 am
I do get your point.  It seems you're missing mine; however.  As an aside, organised tours aren't my cup of tea either.  I prefer to find and explore on my own.

Erik summed it up quite nicely in his last comment.  Of course I want to understand the limits of my equipment (and I do) but I'm not going to waste time replicating DxO or DPReview or anybody else's tests to try and do it.  And I'm certainly not going to set out to try to prove DxO or other test sights wrong.  And most certainly not going to do it while on vacation.  My interests in the limitations of my gear are around practical uses.  Like many, I'll research new gear by looking at what I feel are credible reviews but those only form part of the buying decision and a minority part at that.  The larger part of the decision making process will come from the real world experiences of people whose opinions I value and my own experience from renting/borrowing before buying or taking a memory card to the store and firing of a bunch of shots in different conditions in store and bringing those back to my office to evaluate.  I've actually been asked to leave a store because the salesperson felt I was taking too many shots with their demo camera.  Apparently he worked on the look but don't touch theory of selling.  ::) 

I also understand that, as I noted earlier, technology improves.  It's not a shock when new equipment is better than previous generation equipment.  It is a disappointment when new is not as good as prior.  It's also a serious disappointment; and a larger one than with respect to the technological aspects, when serious design, firmware programming and manufacturing QC problems plague a manufacturer.  If a camera fails in the field it doesn't matter how good its DR is.  If you can't focus a camera in the field, it doesn't matter how good its DR is.  If a camera's mirror falls off in the field it doesn't matter how good its DR is.

So, in conclusion, I'm far more concerned with the practical aspects of what a camera is capable of than the theoretical. 


Hhmm! I'm not sure you did get my point. All my tests are done for practical reasons as an aid to best use my equipment, or to help me select a camera. The tests I quoted in Chiang Mai were done before DXOMark existed and were carried out to help clarify some confusion between absolute or engineering DR specifications, and useful DR that is subjectively acceptable.

On a later trip to Thailand, I also spent the equivalent of a whole day comparing the new Nikon D3 with my old 5D at the main Nikon store in Bangkok. That test was also done before DXOMark existed. I did that in order to check for myself the incredible claims being made at the time that the high-ISO performance of the D3 was up to 2 stops better than any other DSLR on the market. If such claims were true, I wanted one. Alas! They weren't true. At ISO 1600 and above, I wasn't able to see more than 1/2 a stop improvement

Perhaps you do not understand that I'm retired and am therefore on holiday wherever I happen to be, in Australia or in Thailand. The cost of living in Thailand is lower than Australia. I sometimes think I would be financially better off if I were to live there permanently. I might then be able to afford expensive cameras.  ;D
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 15, 2010, 10:58:01 am
Hi!

Whats your main wish? Better DR or usable histograms?

There are two ways to increase DR, one is to increase full well capacity, the other is to reduce read noise. The second option improves DxO ratings but may have little effect in normal photography which is dominated by shot noise, at least in my humble opinion.

Usable histograms would help us to really expose to the right and improve photon statistics.

The look of the noise also matters, some noise is worse than others.

Best regards
Erik

You might be right Erik, but I'm a bit doubtful that we've reached that stage of development where all parts of the image, in all circumstances, are dominated by shot noise in the latest cameras such as the D7000 and K-5.

Even if it is true, that shot noise dominates, that does not necessarily mean there is no room for improvement, does it? For example, if total noise at a particular signal level consists of 55% shot noise and 45% readout noise, including other noise, such as traces of dark-current and fixed pattern noise, then one could claim that shot noise dominates.

However, if we reduce the 45% component to 25%, for example, we will have increased dynamic range, is that not so?

Another issue, about which I admit I'm a bit hazy, is the quantum efficiency of the silicon photo-diodes, or pixels. As I understand, the sensels gather a charge as a result of photons knocking off electrons in the silicon. If a pixel has a full-well capacity of 30,000 electrons, the quantum efficiency will determine how many photons were required to create that charge. If the pixel has a QE of 50%, then 60,000 photons would be required to create that maximum full-well charge of 30,000 electrons. Is this not so? I confess, I'm no expert in this area, but this is how I understand it. Perhaps Bill Janes can comment.

If the the QE of the sensel is increased, even if all other factors remain the same, the useable DR of the sensor will also be increased, will it not?

As I see it, shot noise (or its causes) exists before the image is captured. It's part of the fabric of reality. The perfect camera would capture an image with no less than its full quota of shot noise, in all its glory. Shot noise is the only noise we want to see. That's reality.
Title: If Dxo is right, shot noise is about all that matters now
Post by: BJL on November 15, 2010, 11:41:32 am
If the DXo results are right about the SNR ratio hitting 1:1 only when one gets a full 14 stops below full well capacity on some recent DSLRs, then for all practical purposes, shot noise in the incoming light is the only noise source of practical significance for such sensors, because read noise has been reduced to a level that is insignificant. Note to Ray: "insignificant" is different from "exactly zero".

Why? Because
1. It seems fairly well established (in all but the obsessive pixel/lab test peeping community) that for normal photographic purposes -- as opposed to aerial mapping, machine inspection, security surveillance, medical imaging and so on -- parts of the image with SNR ratio below 10:1 are rather poor, and below about 5:1 is garbage that should be left hidden in the deep shadows of the final displayed image. And to get SNR due to shot noise alone down to 5:1 requires at least 5^2 photons detected, or 25e- of signal. (There is no hint of more than 1e- per detected photon in these sensors, so I will assume detected photons = photo-electrons from now on. More than 1e- per photon would make the dominance of shot noise over read noise even greater.)
2. The well capacity of the photosite sizes in those sensors cannot be more than about 30,000e-: it if were, base ISO speed would be lower than it is. So 14 stops below full is a signal of no more than about 30,000e-/2^14, about 2e-, and if SNR=1 at that level, the read noise is no more than about that same 2e-. (This fits with measurements from other sources of under 3e- for some recent Canon sensors with larger photosites.)
3. For signal of less than 25e-, the results are garbage that needs so to stay in very dark parts of the displayed image, and nothing much can be done about that.
4. At 25e- signal, shot noise is 5e, and adding at most 2e of read noise in RMS fashion gives at most sqrt(5^2+2^2) = 5.4, reducing SNR by less than 10% from 5:1 to 4.63:1: from "bad" to "very slightly worse". This is very unlikely to have any significant visual consequences!
5. As you move above 25e- to more useful signal levels, the contribution of 2e- or less of read noise becomes even less significant. For example, to get the 10:1 local SNR often described as minimally acceptable requires at least 100e- of signal, and adding 2e- of read reduces the SNR only 2%, from 10:1 (shot noise only) to 9.8:1 (shot + read).

Given the evidence from tests on other (Canon CMOS) sensors suggesting comparably low read noise levels (<2e-), and given that for some years special read-out methods in some technical devices has been capable of getting read noise below 1e- RMS, the idea of 2e- read noise is not at all crazy, so maybe these DXo results are for real.

But the "tonal range" measure at DXo seems far more relevant as a predictor of perceived image quality, and it is far lower: 9 stops or less.
Title: Re: If Dxo is right, shot noise is about all that matters now
Post by: Ray on November 15, 2010, 11:01:01 pm
If the DXo results are right about the SNR ratio hitting 1:1 only when one gets a full 14 stops below full well capacity on some recent DSLRs, then for all practical purposes, shot noise in the incoming light is the only noise source of practical significance for such sensors, because read noise has been reduced to a level that is insignificant. Note to Ray: "insignificant" is different from "exactly zero".

Why? Because
1. It seems fairly well established (in all but the obsessive pixel/lab test peeping community) that for normal photographic purposes -- as opposed to aerial mapping, machine inspection, security surveillance, medical imaging and so on -- parts of the image with SNR ratio below 10:1 are rather poor, and below about 5:1 is garbage that should be left hidden in the deep shadows of the final displayed image. And to get SNR due to shot noise alone down to 5:1 requires at least 5^2 photons detected, or 25e- of signal. (There is no hint of more than 1e- per detected photon in these sensors, so I will assume detected photons = photo-electrons from now on. More than 1e- per photon would make the dominance of shot noise over read noise even greater.)
2. The well capacity of the photosite sizes in those sensors cannot be more than about 30,000e-: it if were, base ISO speed would be lower than it is. So 14 stops below full is a signal of no more than about 30,000e-/2^14, about 2e-, and if SNR=1 at that level, the read noise is no more than about that same 2e-. (This fits with measurements from other sources of under 3e- for some recent Canon sensors with larger photosites.)
3. For signal of less than 25e-, the results are garbage that needs so to stay in very dark parts of the displayed image, and nothing much can be done about that.
4. At 25e- signal, shot noise is 5e, and adding at most 2e of read noise in RMS fashion gives at most sqrt(5^2+2^2) = 5.4, reducing SNR by less than 10% from 5:1 to 4.63:1: from "bad" to "very slightly worse". This is very unlikely to have any significant visual consequences!
5. As you move above 25e- to more useful signal levels, the contribution of 2e- or less of read noise becomes even less significant. For example, to get the 10:1 local SNR often described as minimally acceptable requires at least 100e- of signal, and adding 2e- of read reduces the SNR only 2%, from 10:1 (shot noise only) to 9.8:1 (shot + read).

Given the evidence from tests on other (Canon CMOS) sensors suggesting comparably low read noise levels (<2e-), and given that for some years special read-out methods in some technical devices has been capable of getting read noise below 1e- RMS, the idea of 2e- read noise is not at all crazy, so maybe these DXo results are for real.

But the "tonal range" measure at DXo seems far more relevant as a predictor of perceived image quality, and it is far lower: 9 stops or less.

Well first let me emphasise that I accept you know much more about physics and mathematics than I do, BJL, so I would hestitate to dispute your calculations.

But it seems to me we have a shortage of hard facts here, upon which to base our calculations. In such circumstances, practical experiments are the preferred option.

I did a Google search in an attempt to find out what the typical QE of modern sensors are, such as the 7D and D7000, and what the full-well capacity may be. Not much luck I'm afraid.

But I did come across a calculation that deduced the full-well capacity of the 7D pixel is 29,500e-. Whether or not that's accurate, I have no idea.

I also came across a Wikipedia entry containing a computer simulation of a series of images that contain only shot noise and nothing else. To quote:
Quote
A photon noise simulation, using a sample image as a source and a per-pixel Poisson process to model an otherwise perfect camera (quantum efficiency = 1, no read-noise, no thermal noise, etc).

Here's the link: http://en.wikipedia.org/wiki/File:Photon-noise.jpg  If you click twice on the image, you'll get a substantial enlargement.

Again, I've no idea if such a simulation is any more accurate than computer modelling that purports to demonstrate that increasing levels of anthropogenic CO2 levels are a serious threat to our well-being.

But for argument's sake, lets assume such simulations and estimates are true. Let's assume that the 29,500e- full-well capacity of the 7D is true. The D7000 with slightly larger photosites and a slightly larger sensor than the 7D, could then reasonably have a full-well capacity in excess of 30,000e-.

Let's call it 32,768e- for ease of calculation. If we start from a mean number of photons across the entire image of just one per pixel, at a given very short exposure, then double the exposure time in a series of 15 steps (1,2,4,8 etc), we arrive at 32,768 photons, after 15 doublings.

We have in effect a 16 EV dynamic range, presuming no additional noise from the camera. Is this correct?

Let's now refer to the Wikipedia simulation, assuming again it's a realistic simulation.

The first image on the second row, consisting of an average of 1 photon per pixel, is terribly noisy, but it's a recognisable image. If the subject matter were more interesting, a print of this image could hang in an art gallery.

"Ladies and gentleman, behold! The first 'one photon per pixel' digital image that has ever been recorded. Minimalism take a back seat."

(Darling! What the heck is he talking about. I don't understand a word of this.)"



Title: Re: Nikon D7000 Dynamic Range
Post by: dimapant on November 16, 2010, 03:48:10 am
We probably all know by now that the DR of the D7000 at base ISO (together with that of the Pentax K-5) trumps every other digital camera on the market, whatever the format.

..........................

Are you really sure?
Did you print already an A2 side by side?

We will throw away all our stuff to get this miracle!

Many thanks for your information.
Title: Re: If Dxo is right, shot noise is about all that matters now
Post by: Riaan van Wyk on November 16, 2010, 12:37:39 pm
(Darling! What the heck is he talking about. I don't understand a word of this.)"

So say I.
Title: lots of 1-bit pixels are OK, if dithered enough, but not for 100% viewing!
Post by: BJL on November 16, 2010, 07:06:26 pm
Ray,
    first, thanks for confirming my rough estimate of about 30,000e-, and yes, I am happy to round up to 2^15=32,768. Which means that 14 stops below full well is 2^15/2^14 = 2 electrons, or two photons counted.

Second, it seems that I need to be careful when talking with you, in case I am misinterpreted. As I have said some time ago, one photon per pixel is just great for the original image recording, and with negligibly low read noise this would be the ultimate way to preserve spatial detail ... if you have enough pixels to dither heavily for display. Because this is exactly what standard B&W film does! It has many billions of photosites, silver halide crystals or clumps thereof, each of which either detects light or does not, and so provides a 1-bit output signal. To get acceptable visual results, you must then print or display at sufficiently high PPI/sufficiently large viewing distance, and so dither those extremely noisy individual pixels into an image that the eye detects as a lower resolution, higher DR, higher SNR image. (This is part of my refutation of the myth that a sensor with too many, too small pixels will have miserable IQ due to low DR: the confounding of per pixel DR and SNR with perceived noise levels.) I have done 100% pixel peeping of B&W film, by staring though a grain magnifying dark-room focusing aid, and the noise and DR ones sees then is atrocious ... but that says nothing about how the prints look, and not measure of a film's per pixel SNR or DR says anything about the DR of the prints.

In case anyone still misses my point, worrying about per pixel SNR and DR is nonsense without reference to pixel count, the PPI at which the image is displayed and to distance at which it is viewed, and such. People are getting "blinded by science" when trying to draw conclusions above IQ from DR measurements like those at DXo.


But I was talking about acceptable perceived noise levels after dithering, and the images you cite already have a lot of that, at least on the original page, as they are downsampled, so that each pixel on screen averages together multiple pixels from the original file, and has more than one photon per screen pixel. And do note the comment there:
Note the rapid increase in quality past 10 photons/pixel.
To which I would add that 10 photons per pixel is still quite nasty, 100 photons per pixel is a still noticeably grainy, like high ISO B&W film, while 1000 photons per pixel and up look fine to me. And at that nasty 10 photons per pixel and up, 2e- RMS of noise is insignificant, as noted in my previous post.

... Let's assume that the 29,500e- full-well capacity of the 7D is true. The D7000 with slightly larger photosites and a slightly larger sensor than the 7D, could then reasonably have a full-well capacity in excess of 30,000e-. ... Let's call it 32,768e- for ease of calculation.

... Let's now refer to the Wikipedia simulation, assuming again it's a realistic simulation.

The first image on the second row, consisting of an average of 1 photon per pixel, is terribly noisy, but it's a recognisable image. If the subject matter were more interesting, a print of this image could hang in an art gallery.
Title: Re: lots of 1-bit pixels are OK, if dithered enough, but not for 100% viewing!
Post by: Ray on November 16, 2010, 11:44:57 pm
Ray,
    first, thanks for confirming my rough estimate of about 30,000e-, and yes, I am happy to round up to 2^15=32,768. Which means that 14 stops below full well is 2^15/2^14 = 2 electrons, or two photons counted.

You're welcome, but I can't really be sure that figure is correct. The source was not authoritative like DXO  :D .

Quote
In case anyone still misses my point, worrying about per pixel SNR and DR is nonsense without reference to pixel count, the PPI at which the image is displayed and to distance at which it is viewed, and such. People are getting "blinded by science" when trying to draw conclusions above IQ from DR measurements like those at DXo.

BJL,
I always assume that whenever these image quality issues arise, whether it be resolution, SNR, color sensitivity or tonal range, the comparisons only apply at close distances, similar to the distance you would read a book.

At greater distances, perhaps the average distance from which one might most frequently view a print hanging on one's wall, many of these qualitative differences become irrelevant.

However, it is a fact, whenever one is attracted by a print on the wall, and one one walks up close to see the detail, one can be disappointed if one sees fuzziness and noise, because that's not 'real', and it's not pretty.

(Perhaps I should rephrase that for the benefit of those who like a clear distinction between the particular and the general. "However, it is a fact, whenever I am attracted by a print on a wall, and I walk up close to to see the detail, I can be disappointed if I see fuzziness and noise.")

I recall when I first encountered the DXOMark website, I overlooked the 'print' option, top/left of the graphs, but I now mostly do my comparisons in that mode.

Initially I was puzzled that the normalised print size used was so small, 8"x12" at 300ppi representing an 8mp image. But DXO explain on their website that this small print size was chosen in order not to exclude too many cameras which might need their output interpolated to reach a larger normalised print size.

Interpolating an image file can raise all sorts of objections and questions relating to the quality of the interpolation algorithm used. As it is, DXOMark results seem to be disbelieved by many who are under the impression that their preferred RAW converter can make the DXO results meaningless. But I find it strange that such people are unable or unwilling to demonstrate this impression with comparison images.

The obvious explanation is that such people are just kidding themselves. Another explanation is that such people are simply not competent to make such comparison images, and do not wish to reveal that fact, or expose their methodology to criticism.

What I gather from DXO's explanation of the 8"x12" normalised print size, is that any print size will deliver the same comparative result (on the graphs) as long as no interpolation is involved. In other words, A P65+ image and a D3X image, both downsampled to 8"x12" size, will have the same relative qualities as described on the graphs in 'print' mode, as a P65+ image downsampled to A2 size, compared with the D3X image at A2 size, because one can make a print from a D3X image at A2 size without interpolation.

Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 16, 2010, 11:56:10 pm
Are you really sure?
Did you print already an A2 side by side?

We will throw away all our stuff to get this miracle!

Many thanks for your information.


Sorry you don't appear to understand that dynamic range is only one attribute of camera performance.

If your purpose is to make A2 size prints which stand up to critical viewing from close up, then a camera with a higher pixel count than the D7000 might be a better choice, such as the Nikon D3X, A900, 5D2, or an MFDB.

In the old days of film, experienced photographers knew that positives, or slide film, had a rather limited DR capability, but often slide film was preferred for various reasons, both esthetic and practical.

However, when the subject has a very high brightness range, as in the example at the end of this post, slide film would clearly not be suitable. Even the Canon 50D was not ideal for this shot because it has insufficient DR capability.

Generally, slide film had a useable DR of 5-6 stops, color negative film about 7-9 stops and B&W film about 9-11 stops.

We now seem to have reached a stage of technological development whereby a fairly modest, lightweight camera such as the D7000 can deliver approximately the same degree of useable dynamic range as a good B&W negative, but has the advantage of color.

Now it's clear that most of the time, for most shots, the dynamic range of any modern DSLR is sufficient. But sometimes it isn't, and on such occasions it can be infuriating having to mess around on the computer with noise-reduction programs trying to make a silk purse out of a pig's ear.

It's also clear that in certain circumstances, if you know what you are doing, you can compensate for camera inadequacy by using techniques such as 'merge to HDR', when the subject has a high brightness range, or stitching multiple shots to achieve a higher resolution image, if you want to make a large print.

However, such techniques usually require the subject to be still. If you or the subject is moving, then such techniques won't work.

Such was the case with the following shot of St Isaac's cathedral in St Petersburg. Not only was the subject moving (the young ladies in the foreground), but I was also moving fairly rapidly whilst sat in a tour coach which was turning around as it left the square. I got a brief glimpse of the scene and quickly raised my 50D to the window and took 3 bracketed shots.

Because of the significant movement between each shot, there's no possibility of successfully merging the 3 shots to HDR.

The best I can do is select the foreground in the shot with the longest exposure, and paste it onto the shot with the shortest exposure, then fix any problems where the two layers overlap. Even then, the foreground is a bit noisy and I've had to apply some noise reduction.

The difference between the longest and shortest exposure in this example is 2.67 EV. The crops demonstrate the quality differences.

The difference between the DR capability of the Nikon D7000 and the Canon 50D is 2.46 EV (according to DXO).

Got it?
Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on November 17, 2010, 12:30:29 am
Ray,

Thanks for providing a good example.

Just a few points. The large dynamic range of negative films comes from saturation behavior in the highlight region. Digital pretty much clips at a certain light intensity, whereas film tends to have a pretty pronounced shoulder. Density still increases with light but much slower. This is essentially a characteristic of digital imaging.

What BJL and I say is that recent wins in the dynamic range may be more related to reduction in readout noise. But at low exposures shot noise will dominate. Shot noise is simple photon statistics, nothing chip designers can do anything about.

Best regards
Erik


Sorry you don't appear to understand that dynamic range is only one attribute of camera performance.

If your purpose is to make A2 size prints which stand up to critical viewing from close up, then a camera with a higher pixel count than the D7000 might be a better choice, such as the Nikon D3X, A900, 5D2, or an MFDB.

In the old days of film, experienced photographers knew that positives, or slide film, had a rather limited DR capability, but often slide film was preferred for various reasons, both esthetic and practical.

However, when the subject has a very high brightness range, as in the example at the end of this post, slide film would clearly not be suitable. Even the Canon 50D was not ideal for this shot because it has insufficient DR capability.

Generally, slide film had a useable DR of 5-6 stops, color negative film about 7-9 stops and B&W film about 9-11 stops.

We now seem to have reached a stage of technological development whereby a fairly modest, lightweight camera such as the D7000 can deliver approximately the same degree of useable dynamic range as a good B&W negative, but has the advantage of color.

Now it's clear that most of the time, for most shots, the dynamic range of any modern DSLR is sufficient. But sometimes it isn't, and on such occasions it can be infuriating having to mess around on the computer with noise-reduction programs trying to make a silk purse out of a pig's ear.

It's also clear that in certain circumstances, if you know what you are doing, you can compensate for camera inadequacy by using techniques such as 'merge to HDR', when the subject has a high brightness range, or stitching multiple shots to achieve a higher resolution image, if you want to make a large print.

However, such techniques usually require the subject to be still. If you or the subject is moving, then such techniques won't work.

Such was the case with the following shot of St Isaac's cathedral in St Petersburg. Not only was the subject moving (the young ladies in the foreground), but I was also moving fairly rapidly whilst sat in a tour coach which was turning around as it left the square. I got a brief glimpse of the scene and quickly raised my 50D to the window and took 3 bracketed shots.

Because of the significant movement between each shot, there's no possibility of successfully merging the 3 shots to HDR.

The best I can do is select the foreground in the shot with the longest exposure, and paste it onto the shot with the shortest exposure, then fix any problems where the two layers overlap. Even then, the foreground is a bit noisy and I've had to apply some noise reduction.

The difference between the longest and shortest exposure in this example is 2.67 EV. The crops demonstrate the quality differences.

The difference between the DR capability of the Nikon D7000 and the Canon 50D is 2.46 EV (according to DXO).

Got it?

Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on November 17, 2010, 01:03:56 am
Hi,

I made some comparisons between APS-C and full frame in A2-prints. The outcome was interesting:

I one case I could not tell the prints apart. In several other cases the difference was small but I could tell the images apart easily at some distance.

The differences in the prints were much smaller than the difference in files.

---

I also made an experiment with downloaded images shot with different cameras. This was a studio setting, a portrait shot with a lot of different cameras.

So I downloaded an image from D3X and Hasselblad H#D50. Comparing the images at actual pixels it was noted that the Hasselblad image had much more resolution in a very small area than the Nikon D3X. The reason of that area being so small was depth of focus. I made an A2 print of both images and showed to two friends who both worked previously at professional labs. Both said that the images were close, one found the Nikon image sharper and the other one found the Hassy image sharper. Myself new from pixel peeping where to look...

That said, the Nikon image was better! This is one of the issues shooting portrait models in studio. Depth of field is very short and the subject is changing all the time.

To sum up:

In my view, very good A2 prints can be done from 12 MP APS-C images. The file from the larger sensor will be significantly better but the difference in the prints will be smaller than what would be expected from pixel peeping the files.

Best regards
Erik Kaffehr


Are you really sure?
Did you print already an A2 side by side?

We will throw away all our stuff to get this miracle!

Many thanks for your information.

Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 17, 2010, 02:05:27 am

What BJL and I say is that recent wins in the dynamic range may be more related to reduction in readout noise. But at low exposures shot noise will dominate.


Erik,
I'm not clear on this. I presume by 'low exposure' you mean fast exposure, resulting in a small amount of light reaching the sensor. In such circumstances, shot noise will be a greater proportion of the signal (but lower in absolute terms than a longer exposure).

Read noise will also be greater as a proprtion of the signal, so at high ISOs noise is a significant problem, both read noise and shot noise.

What has tended to happen with modern DSLRs, is that the underexposed image at any ISO higher than base, is amplified in its analog state so that it emulates in signal strength the correctly exposed image at base ISO.

Now the amplified signal also amplifies any noise currently present, as well as introducing amplifier noise. That's unavoidable. But the benefit lies in the further signal processing, up-chain (in-camera), before the signal is eventaully written to the memory card.

Such further noise introduced by such processing (A/D conversion, dark frame subtraction, whatever), becomes less proportionally than it otherwise would be.

That's my understanding. Correct me if I'm wrong.

What appears to have happened with the current D7000 and K-5, is that the analog boost to the signal occurs at base ISO to create a larger signal than results in other cameras at base ISO.

As a consequence, the high ISO of the D7000 is no better than competing models, such as the D60 or 7D. But the low ISO performance actually is better by a noticeable margin.

This is no doubt an oversimplified interpretation. Perhaps Emil Martinec could clarify.





Title: Re: Nikon D7000 Dynamic Range
Post by: dimapant on November 17, 2010, 07:54:53 am
Sir,
now is clear and I thank you again for your accurate information.

Best regards

I am new on the forum, sorry: this message is for RAY, for his kind explanation on Dynamic range in answer to my question
Title: Re: Nikon D7000 Dynamic Range
Post by: dimapant on November 17, 2010, 08:04:22 am
Sir,
many thanks also to you for your kind comparison.

I had some doubts about the capability of a Dx or APC forrmat to provide good performances on large (for me) print like A2 format.

I have to revise my opinions and try, as a small camera is quite flexible from the operative point of view, and now is becoming very attractive.

Best regards

Sorry for my bad management of the answers: this message is for Mr EriKKaffehr, for providing me explanation on A2 prints by APC format
Title: Re: Nikon D7000 Dynamic Range
Post by: FranciscoDisilvestro on November 17, 2010, 09:41:33 am
If read noise is so low that even at base ISO the dynamic range is limited by shot noise, then ISO could well be a metadata if you shoot RAW. ISO variation as Analog amplification of the signal will not have any benefit. Even out of Camera Jpegs could be processed according to this metadata, as in the case of White Balance
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 17, 2010, 07:46:10 pm
I notice at DPreview there are a few example images showing noise and detail differences in 'raised' shadows, comparing identical scenes taken with the 60D and D7000. I'm not sure how reliable such examples are.

However, the magnitude of such differences seem to be similar to the differences clearly apparent in the cropped sections of my sunset shot of St Isaac's in St Petersburg, comparing exposures with the 50D that differ by 2.67 stops.

There's a clear implication here that the higher DR of the D7000 claimed by DXO really does translate to a pratical increase in useful dynamic range, compared with Canon DSLRs, notwithstanding claims that such increased performance is already limited by shot noise.

This really is a mixed blessing for me. I'd prefer it to be true that any DR advantage of the D7000 is a fiction as a result of shot noise limitations. I could then quite happily buy a 60D without the feeling that maybe I was depriving myself of some 'occasionally desired' increase in DR capability. I have only one Nikkor lens, the 14-24/2.8.

Will someone please show me some comparison shots of a scene of extremely high SBR, taken with flawless technique, using the D7000 and D60, demonstrating that the theoretical DR advantage of the D7000 is of no practical value.  ;D
Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on November 18, 2010, 01:21:39 am
Hi,

I wanted to post you these links but "PBase" was unavailable yesterday:

Here are crops from A900 (FF) and A700 (DX)
http://www.pbase.com/ekr/image/107619976/original

And here are scanned crops from approximately A2 size prints:
http://www.pbase.com/ekr/image/107823207/original

Printing was done from Lightroom on Epson SP3800, at 480 PPI and normal sharpening for glossy. The prints were scanned at 300 PPI on a cheap Canon scanner.

I had a couple of friends check the images, and no one could tell them apart. That said I made similar tests with other images and I could clearly tell A2 prints apart.

I mostly use full frame, and regard it as a good buy. Image quality is certainly better with larger sensor, but APS-C size may be good enough.

The processing pipeline is very important. I'd say that correct capture and output sharpening has a great significance for print quality.

Best regards
Erik


Sir,
many thanks also to you for your kind comparison.

I had some doubts about the capability of a Dx or APC forrmat to provide good performances on large (for me) print like A2 format.

I have to revise my opinions and try, as a small camera is quite flexible from the operative point of view, and now is becoming very attractive.

Best regards

Sorry for my bad management of the answers: this message is for Mr EriKKaffehr, for providing me explanation on A2 prints by APC format
Title: Re: Nikon D7000 Dynamic Range
Post by: dimapant on November 18, 2010, 06:03:55 am
Hi,

I wanted to post you these links but "PBase" was unavailable yesterday:

Here are crops from A900 (FF) and A700 (DX)
http://www.pbase.com/ekr/image/107619976/original

And here are scanned crops from approximately A2 size prints:
http://www.pbase.com/ekr/image/107823207/original

Printing was done from Lightroom on Epson SP3800, at 480 PPI and normal sharpening for glossy. The prints were scanned at 300 PPI on a cheap Canon scanner.

I had a couple of friends check the images, and no one could tell them apart. That said I made similar tests with other images and I could clearly tell A2 prints apart.

I mostly use full frame, and regard it as a good buy. Image quality is certainly better with larger sensor, but APS-C size may be good enough.

The processing pipeline is very important. I'd say that correct capture and output sharpening has a great significance for print quality.

Best regards
Erik



Impressive!
They are the same, you cannot tell which one is coming from.
Good News!

Many thanks and best regards.

Title: where and how to improve Dynamic Range
Post by: BJL on November 18, 2010, 06:29:09 pm
... recent wins in the dynamic range may be more related to reduction in readout noise. But at low exposures shot noise will dominate. Shot noise is simple photon statistics, nothing chip designers can do anything about.
Agreed. For one thing, "not enough DR" is often said when the problem is not enough highlight headroom above the midtone exposure level, and that is all about (a) giving the sensor enough exposure to gather enough photons from the midtones and shadow regions with significant detail to overcome shot noise, and (b) the sensor then being able to handle the high photon counts in the highlights.
A standard recommended by Kodak is that a 40:1 SNR in the mid-tones gives excellent IQ while 10:1 is minimally acceptable, and my experience indicates that somewhere around 20:1 is the threshold for "quite good". At all these levels, shot noise dominate over the 3e- or less read noise of modern DSLR CMOS sensors (and even more so in modern compacts, whose sensors have even lower read noise in electron counts) because 10:1 needs at least 100e- of signal and so 10e- RMS shot noise, and 40:1 requires at least 1600e- signal and 40e- RMS of shot noise. Normal highlight handling only needs about 3 stops or well capacity a bit under 10 times midtone signal so even 40:1 SNR only needs a 6,000e- well capacity, but if one asks for five stops (following the only zone system idea of zone 5 for midtones, zone 10 or above max), one needs to be able to handle 2^5=32 times the midtone signal, or 51,200e-. [Aside: dithering or downsampling can reproduce this from more, smaller photosites so that for example twice as many pixels as needed for resolution each with half that target well capacity, or 25,600, would work about as well for this.]

That 40:1 SNR and 5-stops are rather strict requirements, as appropriate for people who worry that the 12 stop DR of modern DMF sensors is not enough. A mere four stops is probably a good amount of head-room most of the time, and my experience suggests that around 500e- in the midtones, giving a bit over 20:1 SNR, is enough to look quite good so long as one is not messing with tone curves to lighten shadow regions substantially. For example, on the D7000, exposure index of ISO 1600 gives about 400e- in the midtones, I think). If so, a well capacity of about 2^4*500=8000e- could be enough "for most purposes of most photographers", as far as highlight handling with normal degree of shadow handling needed.

Maybe it is a pity that the only sensor technology that tried to expand highlight headroom by effectively increasing maximum photon count far beyond the normal limits of well size, Fujifilm's SuperCCD SR, has failed in the DSLR marketplace. Or maybe that just shows that some of us are worrying about highlight headroom and DR way too much, and should get back to the time-honored basics of photographic discussions: arguing about lenses!
Title: Re: where and how to improve Dynamic Range
Post by: bjanes on November 18, 2010, 09:24:32 pm
Normal highlight handling only needs about 3 stops or well capacity a bit under 10 times midtone signal so even 40:1 SNR only needs a 6,000e- well capacity, but if one asks for five stops (following the only zone system idea of zone 5 for midtones, zone 10 or above max), one needs to be able to handle 2^5=32 times the midtone signal, or 51,200e-

A nice analysis, but one problem with applying the zone system to digital photography is that there is only a 2.5 stop difference between mid-gray (18% sensor saturation) and highlight saturation, not the 5 stops that one would expect. Placing the highlights 0.5 EV below saturation gives 3 EV headroom above middle gray, which would then correspond to 12.7% saturation. This corresponds to the ISO saturation spec for digital sensor rating. IMHO, allowing 5 stops is not proper ETTR exposure.

BTW, what do you regard as the the minimum SNR for acceptable shadow detail in determining photographic DR?

Regards,

Bill
Title: Re: Nikon D7000 Dynamic Range
Post by: ejmartin on November 18, 2010, 09:33:56 pm
Discussions of SNR should also take into account that SNR varies with spatial frequency.  SNR of 40 at 1000 lph is quite different from SNR=40 at 4000 lph.
Title: Re: Nikon D7000 Dynamic Range
Post by: BJL on November 18, 2010, 10:48:04 pm
A nice analysis, but one problem with applying the zone system to digital photography is that there is only a 2.5 stop difference between mid-gray (18% sensor saturation) and highlight saturation, not the 5 stops that one would expect.
A clarification: I know that there is only 2.5 stops from 18% reflectance to 100%, but was thinking of extreme cases where metered mid-tones are far lower, like having shadows on the main subject that one want to print at middle gray but something brightly sunlit elsewhere in the scene. The base ISO standard allows a bit over three stops above mid-tones, a luminosity factor of 170/18 IIRC (to allow for a main subject darker than 18% reflectance, or somewhat shadowed?), but some people complaining about blown highlights clearly want more at times. My five stops was a rather arbitrary value chosen to be generous to that wish, for cases where exposing to put the highlights just below saturation (ETTR?) places a dimly lit main subject well below 18% of maximum subject brightness. If in that situation someone still wants an excellent 40:1 SNR on the shadowy main subject, big well capacities are needed --- though I suspect that this need is far rarer in real life than in gear-head forum discussions. (I personally avoid having the main subject more than four stops below highlights that cannot be allowed to "white-out", by adjusting composition, because I have never succeeded in getting nice prints in that situation.)
Title: Re: where and how to improve Dynamic Range
Post by: Ray on November 18, 2010, 11:22:46 pm
Agreed. For one thing, "not enough DR" is often said when the problem is not enough highlight headroom above the midtone exposure level, and that is all about (a) giving the sensor enough exposure to gather enough photons from the midtones and shadow regions with significant detail to overcome shot noise, and (b) the sensor then being able to handle the high photon counts in the highlights.
A standard recommended by Kodak is that a 40:1 SNR in the mid-tones gives excellent IQ while 10:1 is minimally acceptable, and my experience indicates that somewhere around 20:1 is the threshold for "quite good". At all these levels, shot noise dominate over the 3e- or less read noise of modern DSLR CMOS sensors (and even more so in modern compacts, whose sensors have even lower read noise in electron counts) because 10:1 needs at least 100e- of signal and so 10e- RMS shot noise, and 40:1 requires at least 1600e- signal and 40e- RMS of shot noise. Normal highlight handling only needs about 3 stops or well capacity a bit under 10 times midtone signal so even 40:1 SNR only needs a 6,000e- well capacity, but if one asks for five stops (following the only zone system idea of zone 5 for midtones, zone 10 or above max), one needs to be able to handle 2^5=32 times the midtone signal, or 51,200e-. [Aside: dithering or downsampling can reproduce this from more, smaller photosites so that for example twice as many pixels as needed for resolution each with half that target well capacity, or 25,600, would work about as well for this.]

That 40:1 SNR and 5-stops are rather strict requirements, as appropriate for people who worry that the 12 stop DR of modern DMF sensors is not enough. A mere four stops is probably a good amount of head-room most of the time, and my experience suggests that around 500e- in the midtones, giving a bit over 20:1 SNR, is enough to look quite good so long as one is not messing with tone curves to lighten shadow regions substantially. For example, on the D7000, exposure index of ISO 1600 gives about 400e- in the midtones, I think). If so, a well capacity of about 2^4*500=8000e- could be enough "for most purposes of most photographers", as far as highlight handling with normal degree of shadow handling needed.

Maybe it is a pity that the only sensor technology that tried to expand highlight headroom by effectively increasing maximum photon count far beyond the normal limits of well size, Fujifilm's SuperCCD SR, has failed in the DSLR marketplace. Or maybe that just shows that some of us are worrying about highlight headroom and DR way too much, and should get back to the time-honored basics of photographic discussions: arguing about lenses!

BJL,
I hope you don't mind if I say that I think you are confusing the issue. We should all know by now that any DR comparisons between images from different DSLRs require the same thorough technique of ensuring a full exposure in both shots (known as an ETTR exposure).

Highlight headroom is an old concept that applied to the film era. Negative film gave more highlight headroom than positive film, and was sometimes preferred for that reason.

With digital, it is assumed that anyone who wishes to compare image qualities from different cameras, whether such qualities be DR, SNR, tonal range or color sensitivity, must compare images that have all been given a 'full' exposure (or ETTR exposure), or such comparisons are not valid.

Comparing images from the same camera that have different exposures, in order to see what visual effect a difference of 1 or 2 stops' exposure may have on the shadows, is fine.
Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on November 19, 2010, 12:08:56 am
Hi,

Could you elaborate on this? Are you discussing perception or measurable quantities?

Best regards
Erik


Discussions of SNR should also take into account that SNR varies with spatial frequency.  SNR of 40 at 1000 lph is quite different from SNR=40 at 4000 lph.
Title: Re: Nikon D7000 Dynamic Range
Post by: Bart_van_der_Wolf on November 19, 2010, 08:16:37 am
Could you elaborate on this? Are you discussing perception or measurable quantities?

Higher spatial frequencies (fine detail) usualy have lower contrast than lower spatial frequencies (coarse detail). Therefore the detail is obscured by the noise faster. That's BTW why I prefer MTFs, they add more info, but they cannot be summarized to a single figure for comparison as easily.

Cheers,
Bart
Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on November 19, 2010, 11:59:06 am
Hi,

I think I got the point now. Modulation transfer is weaker at high frequencies, so the 'S' in the SNR is smaller, correct?

Best regards
Erik



Higher spatial frequencies (fine detail) usualy have lower contrast than lower spatial frequencies (coarse detail). Therefore the detail is obscured by the noise faster. That's BTW why I prefer MTFs, they add more info, but they cannot be summarized to a single figure for comparison as easily.

Cheers,
Bart
Title: Re: Nikon D7000 Dynamic Range
Post by: Bart_van_der_Wolf on November 19, 2010, 12:10:39 pm
Modulation transfer is weaker at high frequencies, so the 'S' in the SNR is smaller, correct?

Yup, as recorded. The original intensities, especially at the higher spatial frequencies, are modified by the optical chain before the sensor can add its noise to the shot noise of the photons that got through.

I'm just assuming that was what Emil was pointing out.

Cheers,
Bart
Title: Re: Nikon D7000 Dynamic Range
Post by: BJL on November 19, 2010, 02:58:15 pm
We should all know by now that any DR comparisons between images from different DSLRs require the same thorough technique of ensuring a full exposure in both shots (known as an ETTR exposure).

Highlight headroom is an old concept that applied to the film era.
My point is actually simpler: many complaints about "inadequate dynamic range" are in reality complaints about "inadequate highlight headroom when I meter the way that I used to with film" because overexposed highlights hit a hard wall with digital that was not there with film. Some sources even try to measure a camera's "highlight DR" and "shadow DR" as separate components, even though the split between the two is a matter of mid-tone placement, which the photographer can adjust.

And as you say, there is a simply-described solution to blown highlights; meter differently, with more attention to the highlights: "ETTL". (Or to get the tolerance for poor exposure choices that negative film can allow, pre-set a negative exposure compensation, and then compensate back up in post.)

That said, this is my point: once highlights are exposed correctly, the dominant limit of noise on IQ will be getting enough light in the main parts of the image, which means getting at least about 500 photons per pixel (or better, somewhere over 1000) in the mid-tones --- and at those photon levels, shot noise overwhelms read noise in modern CMOS sensors, all the way down to three or more stops below the mid-tone subject matter of the scene, and anything darker than that will, in virtually all "artistic" photography [as opposed to surveillance, medical, astronomical etc.] will be printed or otherwise displayed so dark that noise is not a visible problem. So read noise is of little significance, unless one plays games like massively lightening deep shadow regions of the mid-tone print levels: may I call this "shadow peeping"?

I was going to say something abut high ISO case that you mentioned in one post, but that is irrelevant now that we agree that the scenario under discussion is exposures that make use of the full well capacity.
Title: Re: Nikon D7000 Dynamic Range
Post by: madmanchan on November 19, 2010, 03:02:57 pm
Correct -- for example, on many modern SLRs if you spot meter an area and take the picture at the recommended exposure (i.e., with the meter needle in the middle), that area will be about 3 to 3.5 stops below sensor saturation. In other words, you could increase the exposure time by ~3 stops before you start clipping.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 19, 2010, 11:21:53 pm
My point is actually simpler: many complaints about "inadequate dynamic range" are in reality complaints about "inadequate highlight headroom when I meter the way that I used to with film" because overexposed highlights hit a hard wall with digital that was not there with film. Some sources even try to measure a camera's "highlight DR" and "shadow DR" as separate components, even though the split between the two is a matter of mid-tone placement, which the photographer can adjust.

Perhaps this was true about 8 years ago before Michael raised the issue of 'expose to the right (of the histogram)' and 2500 threads ensued, over the years, exploring the concept in ever more detail.

I get the impression that most people still shoot in jpeg mode (even with DSLRs) and they mostly shoot subjects which generally make no special demand on the DR capability of their camera and therefore have no complaints about the DR limitations of their camera, assuming such people even understand what DR means.

Speaking for myself, I would say I have a greater number of spoiled shots as a result of blown highlights than spoiled shots as a result of shadows with unacceptable noise. But of course, a concern for one influences the other. A concern for achieving the best shadow detail can lead one to inadvertently overexpose. A concern to avoid overexposure can result in actual underexposure with the consequence of noisier shadows that one would otherwise get.

For this reason I frequently have my camera set on autobracket mode, because memory is so cheap and because the rated 'potential shutter actuations' of modern DSLRs is so high (typically 150,000). What have I to lose?

Quote
That said, this is my point: once highlights are exposed correctly, the dominant limit of noise on IQ will be getting enough light in the main parts of the image, which means getting at least about 500 photons per pixel (or better, somewhere over 1000) in the mid-tones --- and at those photon levels, shot noise overwhelms read noise in modern CMOS sensors, all the way down to three or more stops below the mid-tone subject matter of the scene, and anything darker than that will, in virtually all "artistic" photography [as opposed to surveillance, medical, astronomical etc.] will be printed or otherwise displayed so dark that noise is not a visible problem. So read noise is of little significance, unless one plays games like massively lightening deep shadow regions of the mid-tone print levels: may I call this "shadow peeping"?

That all sounds very reasonable, JBL, but again I think we're slipping into a modern equivalent of the 'horse's mouth' parable. (Let's attempt to find out how many teeth a horse has through appeal only to authority, instead of checking the hard facts for ourselves.)

The testing that I've done with my own equipment would suggest that what you write above is either, simply not true, or if it is true, there are other significant factors which are being overlooked. Those other factors may be, for example, that read noise and shot noise are not the only sources of noise, even though they may be the single most significant sources, or it may be the case that the eye, being less sensitive to detail and noise in the shadows, can accept shot noise in far greater proportions to the signal than would result in a patch on the sensor with an average of 500 photons per pixel, which I really don't think is at all applicable to deep shadows.

For example, in an area of midtones where the pixels might have a mean average of 500 photons per pixel, the average shot noise would be about 22 photons per pixel. Is this correct?

22 photons per 500?? That's only 4.4%. If shot noise overwhelms read noise at this level, we're still only looking at something less than 8.8% total noise within this tonal range. This is not relevant for even modestly deep shadows.

The testing I'm thinking of, that's relevant here, was carried out shortly after I bought a Canon 20D a few years ago. I'd become rather dissatisfied with the rather limited high-ISO capability of the D60, and the 20D was orders of magnitude better.

I'd read on the old Rob Galbraith forum that it was always better to raise ISO than underexpose at base ISO. This was not such a big deal with the D60. An ETTR exposure at ISO 400 was hardly better than the same exposure at ISO 100, after using EC in ACR to raise the levels.

I decided to check this new performance of the 20D at high ISO for myself, taking two shots of the same high-SBR scene at equal exposure, the exposures being just right for an ETTR at ISO 1600. Of course the exposure when used at ISO 100 became a 4-stop underexposure.

I raised the shadows of the ISO 100 shot in ACR, converting both images without sharpening or noise reduction, and to my astonishment the ISO 1600 shot was so much better across the entire tonal range. Whilst the greatest improvement was observable in the shadows, there was a lesser, but still noticeable improvement in the midtones and upper mid-tones, in the ISO 1600 shot.

Now some of you may be thinking, so what! This is old hat. We all know that it's better to use the higher ISO rather than underexpose at base ISO.

But here's the rub. Not with the D7000. There's no image quality advantage in using a higher ISO as an alternative to underexposing at base ISO. So what? You're probably thinking again.

If we refer to the DXOMark graphs, comparing the D7000 with the 20D in 'screen' mode (ie. pixel level), we find that at ISO 1600 a D7000 image, cropped to the 8mp of the 20D is as good in all parameters that DXO measure, SNR, DR, tonal range & color sensitivity.

Or, to put it another way, the image which was underexposed by 4 stops in the 20D at ISO 100 and which looked significantly noisier than the analog-boosted image at ISO 1600 in the 20D, will not look noisier in the D7000 when underexposed 4 stops at ISO 100. It will look about the same as the analog-boosted ISO 1600 shot from the 20D, ie. much improved.

Of course the D7000 has double the pixel count of the 20D and that fact provides for an over all better performance than the 20D at equal image or print size. That's another issue. To see the effects of that, click on 'print' mode on the DXOMark charts. The 20D is left behind in all respects.

Now some of you are probably protesting that the 20D is old technology. This fact I find quite interesting. The 20D is old technology and newer models since then have boasted many useful improvements, but not it seems at the pixel level, with the exception of the most recent 1DMK4 which, at the pixel level, has 2/3rds of a stop greater DR than the 20D at ISO 3200, but only at ISO 3200 (and probably beyond if one extrapolates the graph for the 20D). At lower ISOs the difference is reduced to 1/2 a stop, the minimum difference that might be of any concern.

In fact the 20D pixel seems to very slightly better, over all, than the 1Ds3 pixel, with regard to all parameters. The 5D2 pixel appears to be sometimes very slightly better than the 20D pixel, but not by a margin that one would notice in practice.

It seems that the 20D pixel represented the pinnacle of Canon technological achievement, until the 1D4 pixel edged ahead in respect of DR. Regarding color sensitivity, tonal range and SNR at 18% grey, there appears to be no improvement over the 20D pixel.

Have I successfully counted the horse's teeth without even sticking my head in the horse's mouth?  ;D


Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 19, 2010, 11:38:55 pm
Correct -- for example, on many modern SLRs if you spot meter an area and take the picture at the recommended exposure (i.e., with the meter needle in the middle), that area will be about 3 to 3.5 stops below sensor saturation. In other words, you could increase the exposure time by ~3 stops before you start clipping.

I tried this technique with my 5D a few years ago. I would have the camera in 'spot meter' mode and search the scene I was about to photograph for the brightest patch, often a white cloud, but sometimes simply a white napkin in a restaurant. I would take an exposure reading of that brightest patch, then increase exposure by 3 stops. It seemed to work without fail, giving me a good ETTR exposure.

Trouble is, a lot of my photography is capturing the moment, which I find difficult enough as it is. Introducung additional concerns such as searching for the brightest patch in a scene, then calculating a 3 stop exposure increase from the spot meter reading of that brightest patch, caused me to miss the moment too often.  :D
Title: Re: Nikon D7000 Dynamic Range
Post by: bjanes on November 20, 2010, 09:48:03 am
Correct -- for example, on many modern SLRs if you spot meter an area and take the picture at the recommended exposure (i.e., with the meter needle in the middle), that area will be about 3 to 3.5 stops below sensor saturation. In other words, you could increase the exposure time by ~3 stops before you start clipping.

Eric,

That is useful information and is consistent with what was reported by the late Bruce Fraser, but one should probably do tests for his own camera. The results would vary with the calibration of the camera's light meter and the ISO rating of the sensor. As far as I know, most camera light meters use the ISO 2721 standard, which gives similar results to ISO 2720 for hand held meters. Otherwise, one would get different results for hand held and built in metering (disregarding lens transmission and lens extension).

However, there is considerable variation in the ISO ratings for sensors. The ISO saturation rating (which is used by DXO) would give 12.7% saturation when exposure is made according to the metered reading, which corresponds to a pixel value of 99.8 in an 8 bit gamma 2.2 space. One can test his own camera by exposing a uniformly illuminated target such as a white wall or gray card and determine sensor saturation. The best way to do this would be to use a program that looks directly at the raw data such as DCRaw, Iris, or Rawnalize.

I did this for my Nikon D3 and got 12.1% saturation, which is 3 stops below saturation. This allows 0.5 EV of highlight headroom and is very close to the ISO saturation standard.  Not everyone uses one of these programs and it is more convenient to use Adobe Camera Raw (for those who use this program). However, there are complications. ACR uses a BaselineExposure offset to compensate for highlight headroom allowed by the camera. For the D3, this is +0.5 EV. In addition, the default tone curve boosts the mid-tones. Using ACR defaults, the AdobeRGB value for this exposure is 146, which is much higher than expected. Using -0.5 EV of exposure and a linear tone curve (sliders on the main ACR tab all set to zero and the point curve set to linear), gives an aRGB value of 97, which is very close to the calculated value of 99.8. Using the default exposure value and a linear tone curve gives a pixel value of 116, which is very close to mid-gray (117). Is this process what you would expect and is it valid for other cameras?

One can determine the ISO speed rating for other sensors from the DXO data. Nikons seem to have ratings similar to the ISO saturation standard, but slightly conservative. The Canon 1DsM3 allows more highlight headroom and the Phase One P65+ gives an entire f/stop headroom.

Regards,

Bill
Title: Re: Nikon D7000 Dynamic Range
Post by: madmanchan on November 22, 2010, 11:27:31 am
Bill, good points, but keep in mind that metering and sensor saturation in the raw data are largely independent of the ISO standards. To put it directly, ISO 12232 (which concerns itself with the determination of exposure index, ISO speed ratings, standard output sensitivity, and recommended exposure index) says nothing about raw image data, and does not even contain the word "raw" in its well-written 24 pages.

Ray, true, one does not always have the luxury "in the field" to obtain optimal exposure. But if you are concerned about dynamic range and extracting the max SNR your sensor has to offer (which is what I gather from this thread topic), then that is precisely what needs to be done.

In reality, with today's cameras, there is a tradeoff between "getting the shot" and "getting optimal exposure" -- which is a shame because the technology exists to do both simultaneously.
Title: Re: Nikon D7000 Dynamic Range
Post by: bjanes on November 22, 2010, 10:01:00 pm
Bill, good points, but keep in mind that metering and sensor saturation in the raw data are largely independent of the ISO standards. To put it directly, ISO 12232 (which concerns itself with the determination of exposure index, ISO speed ratings, standard output sensitivity, and recommended exposure index) says nothing about raw image data, and does not even contain the word "raw" in its well-written 24 pages.

Eric,

You know quite a bit more about these matters than I do, and I don't have the 24 page document, but I understand that the ISO saturation standard, at least the 1996 version, did talk about sensor saturation. See the DXO (http://www.dxomark.com/index.php/en/Learn-more/Understanding-DxOMark-Database/Measurements/ISO-sensitivity) explanation of how they determine sensor sensitivity. They claim to be using the ISO Standard 12232.

Regards,

Bill



Title: Re: Nikon D7000 Dynamic Range
Post by: BJL on November 23, 2010, 05:25:29 pm
I decided to check this new performance of the 20D at high ISO for myself, taking two shots of the same high-SBR scene at equal exposure, the exposures being just right for an ETTR at ISO 1600. Of course the exposure when used at ISO 100 became a 4-stop underexposure.

I raised the shadows of the ISO 100 shot in ACR, converting both images without sharpening or noise reduction, and to my astonishment the ISO 1600 shot was so much better across the entire tonal range. Whilst the greatest improvement was observable in the shadows, there was a lesser, but still noticeable improvement in the midtones and upper mid-tones, in the ISO 1600 shot.

But here's the rub. Not with the D7000. There's no image quality advantage in using a higher ISO as an alternative to underexposing at base ISO.
Ray, what you seem to have shown is that the DR of the D7000 allows one to survive 4 stops of underexposure while the D20 did not. How important is this? Do you make that sort of exposure mistake often,or ever? It certainly does not refute my suggestion that once read noise levels are as low as in the D7000, read noise is irrelevant, because all you are comparing to is another, older, inferior camera whose total read noise at low ISO (I actually mean all noise other than shot noise) is far higher than in the D7000, and high enough to be problematic ... but maybe even then only problematic if one underexposes by four stops and then raises the levels by four stops, bringing severely underexposed shadow regions up to mid-tone levels.

And I have a hunch as to what is going on with the 20D,and even in more recent Canon DSLRs: at ISO 100, the noise floor is probably dominated by sources arising after ISO gain is applied (which Canon seems to do on the sensor): low ISO noise is largely produced in the subsequent signal transportation and/or in A/D conversion. What the D7000 has perhaps achieved is what MF backs have more or less been doing for some time in a different way: making variable analogue gain (ISO adjustment before ADC) rather irrelevant, by producing digital output that records the full SNR of the signal from the photosites. Exposure level can thus be chosen after the fact as a digital adjustment on RAW files. This has been easier for MF backs, because ISO gain cannot be applied anyway until the signal has been moved off the sensor, by which time almost all read noise is already present, and so all that is needed is a good enough, high bit-count, low-noise ADC.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 23, 2010, 09:40:54 pm
Ray, what you seem to have shown is that the DR of the D7000 allows one to survive 4 stops of underexposure while the D20 did not. How important is this? Do you make that sort of exposure mistake often,or ever? It certainly does not refute my suggestion that once read noise levels are as low as in the D7000, read noise is irrelevant, because all you are comparing to is another, older, inferior camera whose total read noise at low ISO (I actually mean all noise other than shot noise) is far higher than in the D7000, and high enough to be problematic ... but maybe even then only problematic if one underexposes by four stops and then raises the levels by four stops, bringing severely underexposed shadow regions up to mid-tone levels.

BJL,
I think you might have missed the significance of the point I was trying to make. Perhaps my comparison was a bit convoluted. I'll try again.

The underexposure of 4 stops at base ISO, whether in the 20D or the D7000, reduces the effective dynamic range of those cameras by 4 EV in those instances. Would you agree?

If we were to choose another scene which included the same tonal range and shadows as in the 4-stop underexposure at base ISO, but in addition included a brighter section (such as a sky with bright clouds) which extended the brightness range of the entire scene by another 4 stops, then we would have an ETTR exposure with both cameras which would likely demonstrate the DR capability of those cameras.

Of course, such an exposure with the 20D at ISO 1600 would then be overexposed by 4 stops, but the quality of those parts of the image that are not overexposed would remain the same as in the previous scenario, ie. better than the same range of tonal values at ISO 100, in the 20D.

However, since we are trying to be precise here, we should try to exclude the fact that the D7000 has double the pixel count of the 20D. Let's avoid as far as possible, distracting and extraneous issues.

DXOMark allows us to compare cameras at the pixel level. To do this in practice with 'real-world' images, in order to verify the relevance and accuracy of the DXO results, we should treat the D7000 as though it is a 'cropped format of a cropped format', with an additional crop factor of 1.4x.

In other words, we should use a focal length of lens that is appropriately wider (than the lens on the 20D), by a factor of 1.4, and an aperture that is appropriately wider by a factor of 1.4, when using the D7000.

In order not to put the D7000 at a disadvantage regarding lens performance, we should use F stops like F8 with the D7000 and F11 with the 20D (or F11 with the D7000 and F16 with the 20D), because the D7000 with its greater pixel density needs a higher resolution lens for the same perceived sharpness. Let's not introduce further extraneous factors of differing resolution, since it is only DR quality we are concerned about here.

Okay! So we've sorted out the practicalities of a fair, objective and meaningful, 'real world' comparison.

I predict the outcome would be:  Image quality in the region of 4 stops below full-well saturation (from both cameras at base ISO), would be better in the D7000 image, than in the 20D image, in accordance with DXOMark test results.

As I've mentioned before, when using all 16mp of the D7000, there's no contest between the D7000 and the 20D. This is not because the 20D is old technology, but because the D7000 is better technology. The 20D pixel is basically as good as the 1Ds3 pixel. The 1Ds3 sensor could be considered as 2.6 20D sensors stitched together and reorganised into a 3:2 aspect ratio. This fact is quite illuminating.

There are certain areas of performance where the 1Ds3 pixel is very marginally better than the 20D pixel, and other areas where the 20D pixel is marginally better than the 1Ds3 pixel, but such differences are of no consequence in practice, at the pixel level.

The main point is that the 1Ds3 pixel is the same size as the 20D pixel and its qualities have not seemed to have improved since the 20D was released. The 20D camera may be old technology, but its pixel is still the equal of any other in the Canon repertoire, with the possible exception the most recent 1DMk4 pixel which appears to be marginally improved in some respects.

Now, for all those who find this very convoluted, I'm afraid I have no special de-convolution algorithm available which you can download to help you clarify the issue. You'll have to search within for the appropriate algorithm.  ;D


Quote
And I have a hunch as to what is going on with the 20D,and even in more recent Canon DSLRs: at ISO 100, the noise floor is probably dominated by sources arising after ISO gain is applied (which Canon seems to do on the sensor): low ISO noise is largely produced in the subsequent signal transportation and/or in A/D conversion. What the D7000 has perhaps achieved is what MF backs have more or less been doing for some time in a different way: making variable analogue gain (ISO adjustment before ADC) rather irrelevant, by producing digital output that records the full SNR of the signal from the photosites. Exposure level can thus be chosen after the fact as a digital adjustment on RAW files. This has been easier for MF backs, because ISO gain cannot be applied anyway until the signal has been moved off the sensor, by which time almost all read noise is already present, and so all that is needed is a good enough, high bit-count, low-noise ADC.

I'm speculating something similar. Put simply, Canon amplify the low-level (underexposed) analog signal at high ISO in order to improve SNR and the general image quality.

Nikon, with the D7000, amplifies the analog signal at base ISO to achieve an extended DR and better image quality in the shadows, which is carried through to higher ISOs when underexposure at base ISO takes place and exposure compensation is subsequently applied in software.

Title: Re: Nikon D7000 Dynamic Range
Post by: BJL on November 23, 2010, 10:13:02 pm
Ray, we are going in circles. My point is that to see the effects of the 14th stop or so of dynamic range, you have to lighten underexposed shadow regions by about for stops. Your example is based on having to use exposure four stops less than usual in order to avoid blown highlights, so that instead of a normal midtone placement about three stops below maximum, the midtones about seven stops below maximum! That means about 1/128 of full well, so about 200e- in the D7000. A midtone exposure that low will cause distinct noise problems in the important midtone areas, mostly due to photon shot noise, so reducing the badness of the greatly lightened deep shadows will probably be the least of your problems for noise effects on overall IQ.  To repeat my point from a previous post, good midtone quality requires getting more exposure there  of about 500 to 1000e- or more, and the only solution to doing that while avoiding blowing of the extreme highlights in your hypothetical example, 7 stops brighter than midtones, is increasing DR through increasing well capacity for highlights, not reducing read noise in the deep shadows.

But perhaps you have real examples where this extreme lightening is needed even with optimal "ETTR" exposure, and is done while also achieving good midtone IQ, rather than severe underexposure for no good reason? "Shadow peeping" examples that merely crop to deep shadow regions and dramatically lighten them while ignoring midtones are not of practical interest.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 23, 2010, 11:19:00 pm
Ray, we are going in circles. My point is that to see the effects of the 14th stop or so of dynamic range, you have to lighten underexposed shadow regions by about for stops. Your example is based on having to use exposure four stops less than usual in order to avoid blown highlights, so that instead of a normal midtone placement about three stops below maximum, the midtones about seven stops below maximum! That means about 1/128 of full well, so about 200e- in the D7000. A midtone exposure that low will cause distinct noise problems in the important midtone areas, mostly due to photon shot noise, so reducing the badness of the greatly lightened deep shadows will probably be the least of your problems for noise effects on overall IQ.  To repeat my point from a previous post, good midtone quality requires getting more exposure there  of about 500 to 1000e- or more, and the only solution to doing that while avoiding blowing of the extreme highlights in your hypothetical example, 7 stops brighter than midtones, is increasing DR through increasing well capacity for highlights, not reducing read noise in the deep shadows.

BJL,
You might be going around in circles, but I'm not. My point is as straight and as linear as the exposure of a sensor.

Four stops underexposure at base ISO on the D7000 results in a maximum (engineering) DR of 9.35 EV, at the pixel level, according to DXOMark.

Four stops underexposure on the 20D at base ISO results in a maximum engineering DR of just 6.95 EV.

Those 6.95 EV of DR have better image quality on the D7000, period. I'm not even considering the extra 3 stops of DR that the D7000 is capable of. Those extra 3 stops might well be crap, of no artistic value, I agree. I'm concerned with the image quality of the 9-11 stops of DR which take the 20D to the engineering limit (and the 1Ds3 also to the engineering limit at the pixel level).

Quote
But perhaps you have real examples where this extreme lightening is needed even with optimal "ETTR" exposure..

Of course I do. I'm a practical man. Did you miss my examples of the St Isaac's Cathedral in St Petersburg, on page 2 of this thread?

The sun was near setting at about 10.30 pm, and almost visible behind the clouds. Avoiding blown highlights in the clouds surrounding the sun was impractical. If I'd reduced exposure even more to achieve this, the midtones would have been even noisier.

These are not deep shadows that are noisy, but the whole foreground.


Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on November 24, 2010, 12:38:25 am
Hi,

I have made a few experiments with HDR in the past year. The experience has mostly been mixed, but more negative than positive.


So, what I try to do is to expand dynamic range. Problem is that we still have a limited dynamic range for display, something like 1:500 on screen and 1:120 in print. What I have found that the real world density range on my cameras (Sony Alpha) is good enough that I can extract shadow detail from an -2EV exposure.  

Messing with HDR doesn't really make the image better, even if I get less noise and better resolution in the shadows. On the other hand it's easy to get unrealistic color with HDR.

HDR: http://echophoto.smugmug.com/Special-methods/HDR/HDR/13306153_DcZHj#966794997_wt4h6 (http://echophoto.smugmug.com/Special-methods/HDR/HDR/13306153_DcZHj#966794997_wt4h6)

Non HDR: http://echophoto.smugmug.com/Special-methods/HDR/HDR/13306153_DcZHj#1002864735_dkeci

My Sony Alpha is not a DR champ by any means, and it has been my experience that there is a lot of good shadow detail in properly exposed DSLR images.

The screen dump below show both images. HDR on left and DNG processed in Lightroom on the right. The DNG image is parametrically processed but with a healthy amount of local manipulation. Tonal separation in the clouds is achieved by generous local application of clarity.

Best regards
Erik

But perhaps you have real examples where this extreme lightening is needed even with optimal "ETTR" exposure, and is done while also achieving good midtone IQ, rather than severe underexposure for no good reason? "Shadow peeping" examples that merely crop to deep shadow regions and dramatically lighten them while ignoring midtones are not of practical interest.
Title: Re: Nikon D7000 Dynamic Range
Post by: BJL on November 24, 2010, 04:54:14 pm
Four stops underexposure at base ISO on the D7000 results in a maximum (engineering) DR of 9.35 EV, at the pixel level, according to DXOMark.
Four stops underexposure on the 20D at base ISO results in a maximum engineering DR of just 6.95 EV.
...
Those 6.95 EV of DR have better image quality on the D7000, period.
Please read again what I said in post #48 in this thread: my skepticism is about whether improving beyond 12 stops of DR at base ISO is significant. So proving an advantage over an older camera offering only about 11 stops of DR is irrelevant.
Quote
Did you miss my examples of the St Isaac's Cathedral in St Petersburg, on page 2 of this thread?
... These are not deep shadows that are noisy, but the whole foreground.
I cannot find any such photo in you earlier posts in this thread; can you given me the link again?
And if it is with that "old, noisy" 20D, it is irrelevant for the reasons stated above. Only if done with a camera giving 12 stops of more of DR at the ISO in use is it relevant to my claim about the lack of benefit in improving beyond 12 stops of DR.  And if the noise is visible "in the whole foreground", that sounds like it visible in the midtones or just a bit below, and then for reasons I have already stated, it is likely to be due to shot noise, not read noise and the root of the problem is too low a maximum photon count, not too much read noise. (Perhaps for the sake of science, you need to get a D7000 and revisit that Cathedral!)
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 25, 2010, 09:04:06 pm
I cannot find any such photo in you earlier posts in this thread; can you given me the link again?


Have you tried logging on before searching, BJL? It seems to be a peculiarity of the new forum software, if you are not logged on you don't see any pictures.

The images demonstrating noisy shadows are in reply #23 and reply#38.


Quote
And if it is with that "old, noisy" 20D, it is irrelevant for the reasons stated above.

BJL, why don't you be clear and state that you don't give much credence to the DXO tests, so we all know where we stand? All the tests that I've carried out, that are relevant to the DXO results, such as testing the DR limits of my 5D, and comparing the high ISO performance of the 5D with the Nikon D3, seem to correspond very closely with the DXOMark results in relation to those cameras. I have no reason to doubt the validity of their testing procedures and the accuracy of their results.

If the 20D is noisy, then so is the 1Ds3. If you were to shoot identical scenes with both cameras, using the same lens at the same aperture, then crop the 1Ds3 image to the same FoV as the 20D image, you would have two indistinguishable photos of the same file size (according to DXO's test results).

Below ISO 800, the 1Ds3 begins to have a very slight DR advantage which reaches a peak at base ISO, where it's 0.3EV better than the 20D. On the other hand the 20D above ISO 800 edges ahead of the 1Ds3 by a similar degree. As regards SNR at 18% grey, tonal range and color sensitivity, the pixels of both cameras appear to be identical, and that also includes the more recent 1DMkIV.

However, the 1D4 appears to have a noticeably better DR than both the 1D3 and 20D at higher ISOs. At ISO 3200 it's a whole stop better than the 1Ds3, so it's clear that Canon have made some improvement at the pixel level in the 1D4.


 
Quote
Only if done with a camera giving 12 stops of more of DR at the ISO in use is it relevant to my claim about the lack of benefit in improving beyond 12 stops of DR.

The benefit of the greater-than-12 stops of DR (of the D7000) is to be found in the 10th and 11th stops. I have never argued that the last two stops of an engineering-type specification of a DR, such as the ones that DXO seem to provide, are useable on a print.

What I do know from my own tests with the 5D and the 20D is that at base ISO detail in the 10th and 11th stops from those two cameras is too degraded to be of practical use. But at ISO 1600, such degraded detail is quite noticebly improved by a worthwhile degree, and not only in the 11th and 10th stops, but the 9th and 8th and so on.

If we accept that the D7000 has a  performance at high ISO at least equal to its competitors, such as the Canon 7D and 60D, but can achieve this image quality without the use of the higher ISO settings, presumably because image quality at base ISO is so darned good, then it follows logically that those 11th, 10th, 9th and 8th stops of DR in the D7000 at base ISO, will be less degraded and more detailed than the same stops in the 60D, 7D, 20D, 1Ds3 and so on, at base ISO.

I'm surprised you seem to be having trouble grasping this point, BJL. I always got the impression you were a very rational, logical and objective sort of guy.

You certainly seem to find access to lots of technical documents detailing sensor specification at the manufacturers'web sites. Perhaps you could do me a favour and explain to me the significance of the 'quantum efficiency' of a photodiode and the relationship between the 'electron charge' and the number of photons required to produce such charge.

For example, we seem to agree that a full-well capacity for the D7000 pixel could be around 32,768 e-.  But a pertinent question might be, 'How many photons were required to be 'absorbed' by the pixel in order to achieve such charge?.

Another pertinent question would be, ''What proportion of photons arriving at the outer surface of the sensor is blocked or absorbed by the various filters before the light even reaches the photodiode?

We know that the Color Array Filter of the Bayer-type sensor absorbs at least half of the light reaching it. The green filter has to exclude both red and blue frequencies, otherwise the pixel wouldn't be green. Furthermore, it is reasonable to assume that other filters such as the AA filter, IR filter and even the slight degree of opacity of the microlenses and filters will absorb yet more light.

Such facts seem significant to me because shot noise is caused by the slightly random and unpredictable arrival of individual photons during any given exposure of the sensor. Such shot noise exists before the photons pass through the various absorbing filters and microlenses. It therefore seems reasonable that the calculations for shot noise (the square root of the mean average of photons collected by the photodiodes) should in fact be applied to the number of photons arriving at the sensor's outer surface. Would you agree or not?

If this is the case (and I'm certainly not asserting that it is), we cannot use the 'electron charge' figure for calculations regarding shot noise.

Consider a situation where the full-well capacity of the D7000 is, for argument's sake, 32,768 e-. The 11th stop down from (and including) full-well capacity should then have a charge of just 32 e-. But that does not necessarily mean that the shot noise is sqrt of 32, or 5.65 photons which represents about 17% of the signal, which is quite high, but in fact may be the sqrt of 100 photons which represents a shot noise of just 10%.

Would you agree? If not, please enlighten me.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 26, 2010, 11:31:59 pm
Hi,

I have made a few experiments with HDR in the past year. The experience has mostly been mixed, but more negative than positive.


Erik,
All the more reason to have a camera with a high DR, to reduce the number of occasions when you might see a need to bracket exposures in order to merge to HDR.

Being aware of a need to bracket exposures in order to increase DR is one thing. Being able to do that successfully is another thing. First, the scene really does have to be stationary. I've bracketed exposures of the Himalayas with camera on tripod, only to discover back home that the very slight breeze causing movement of the tall grass in the foreground, and the slight movement of the distant clouds in the background, has made the merging to HDR process too difficult to bother with.

In such circumstances I choose the exposure which is closest to an ETTR and do my best to cover up any noise which might be apparent in the shadows.

Having successfully merged different exposures to HDR without any 'misalignment' of detail, there's sometimes a further problem of making the right 'tone-mapping' adjustments to get the image looking natural.

In my view, this is partly because one is faced with a whole new system of tonal adjustments which are different from the regular adjustments in ACR that one might be familiar with.

Another issue is the number of auto-bracked shots the camera is capable of. I've often found with Canon cameras that the maximum of +/- 2EV with just 3 shots is not ideal for merging to HDR. The extension of 4 stops of DR may be sufficient, but the gap of 2EV between each exposure may not produce in the best result. 5 frames with a 1EV difference between shots would be better.


Quote
So, what I try to do is to expand dynamic range. Problem is that we still have a limited dynamic range for display, something like 1:500 on screen and 1:120 in print. What I have found that the real world density range on my cameras (Sony Alpha) is good enough that I can extract shadow detail from an -2EV exposure.

I've noticed, Erik, that you've mentioned this factor before, quite frequently, implying that in some way the DR limitations of the print medium makes a high DR capability in the camera irrelevant or less relevant.

This is simply not true if one knows how to process an image in Photoshop. It's possible to display, in a natural way, the full dynamic range on the print of any correctly exposed high-SBR scene, even if the scene encompasses a whopping 20 stops of DR.

How is this possible? First, let me explain how the eye perceives a scene. (In simple terms so I can understand it myself).

The eye has a surprisingly narrow field of view as regards discernment of detail. Peripheral vision tends to give us the impression that the eye's FoV is quite wide, but peripheral vision is mainly good for the detection of movement. It's totally hopeless for the discernment of detail. To see all the detail in a scene that may be captured even by a moderately wide-angle lens, we have to shift our gaze from side to side, the equivalent of image stitching in a camera.

A similar situation applies to the eye's DR capability. When perusing a scene, we find in one moment we can see lots of detail in the white, fluffy clouds in the sky, then a fraction of a second later, as we shift our gaze to some shadows at the foot of a nearby tree, we can see leaf litter and lots of fine detail in the dark shade which really doesn't look all that dark anyway, but would look very dark if we were to photograph the scene with a single shot, exposing for the clouds.

It's easy to get the impression that the eye has a very wide DR capability. In a sense, it does, but only because it has the capability of bracketing exposures. The pupil of the eye, which is similar to the aperture of a camera lens, can dilate and contract in a fraction of a second in order to accommodate changing brightness levels.

Sometimes, when the change in brightness is extreme, it may take several seconds for the eye to adjust, such as coming out of a darkened cinema into the bright sunlight. But normally, a shift in brightness of just a few stops is almost instantly accommodated by a change in the aperture of the pupil.

So basically, if we compare the eye with a camera, using camera terminology, the eye is continually performing image stitching to widen its FoV, and continually bracketing exposures in order to increase its dynamic range.

A single shot from a camera, any camera, even the D7000, cannot compete with the eye as it's normally used with its continual gaze-shifting and changes of aperture.

Okay! All that must be crystal clear to you all, so let's move on to the print. How do we portray on a print, with its very limited DR, the full DR of a 20 EV scene?

Well, I'm no expert on the potential of the myriad of processes and techniques in Photoshop. I'm sure Jeff Schewe could make me look like a complete novice in that respect.

But there are a few very simple techniques that work quite well for me. First, the Shadows/Highlight tool. You need to be in advanced mode of course, but this is a tremendously useful feature in Photoshop for quick adjustments of balance between shadows and highlights. If you need more extreme adjustments, you can repeat the process.

Another simple technique (you must have noticed, I like simplicity), is to select with the lasso tool any area on the image you want to treat separately, feather appropriately (30, 50 or 100 pixels), then apply whatever adjustments you think appropriate.

By such processes, you can achieve on the print, the full detail of a bright cloud in the sky, and the full detail in the shadows at the foot of a tree in the foreground, if your camera has sufficient DR or, if you bracket exposures and merged to HDR.



Quote
Messing with HDR doesn't really make the image better, even if I get less noise and better resolution in the shadows. On the other hand it's easy to get unrealistic color with HDR
.

You are confusing the 'subjective' with the 'objective' here. The term, 'better', without a qualifying description, is about as subjective as one can possibly get. However, 'less noise' is a comparative matter which is either true or false. If it is determined to be true, objectively, through the sorts of measurements that DXO make, but subjectively one cannot see it, then one can reasonably surmise a number of possible causes.

(1) One doesn't know what 'visual' noise is and therefore cannot recognise it.

(2) The differences in noise are so small that they are irrelevant in practice, or beyond the threshold of normal discernment.

(3) The display medium, monitor or print, is not of sufficient quality, or not sufficiently well-calibrated, to enable the observation of such differences.

(4) The observer has a medical or genetic problem with his eyesight.

Of course, there may be other reasons of a more psychological nature, which perhaps we should not dwell upon. People can have 'blind spots'. Sometimes seeing the truth is too painful, so we bury our head in the sand.

Sometimes people identify so strongly with their camera equipment that it becomes part of their personality, so any criticism of their camera equipment is viewed as a criticism of themselves, their taste and their judgement.

So, if camera A has better high-ISO performance than camera B, then someone who owns camera B, of which he is very proud and which symbolizes his good taste and discernment, may first try to dispute the validity of the tests that imply that camera A has better ISO performance.

Having failed to convincingly win the argument that the tests are invalid or inaccurate, because of mounting photographic evidence that camera A really does have better high-ISO performance than camera B, the owner of camera B may then resort to other tactics to preserve his self-esteem.

A typical response might be, "I never use high ISO, so it's irrelevant." Or, in the case of camera A having a wider DR than camera B, "I'm not interested in pixel-peeping shadows. The DR of my current camera B is quite sufficient."

One sees many examples of such attitudes on DPreview.

By the way, Erik, your example images of HDR do not appear in IE when I click on them. There's something wrong.

Cheers!
Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on November 27, 2010, 04:16:24 am
Hello Ray,

Here is another link to the HDR stuff. It works for me: http://echophoto.smugmug.com/Special-methods/HDR/HDR/

I have not tested with Internet Explorer as I don't have it on my Macs.

Regarding HDR I planned an article on "doing things with multiple images" discussing stitching, HDR, and infinite DOF. Unfortunately I got stuck on HDR. The reason for that is that I failed to come up with any good example where HDR is of significant benefit, and the main reason is the cameras having enough DR.

There are some points you may miss in your lengthy response. The major one, as I see it, is that an HDR image is not in a normal representation but using some more exotic data representation, like floating point or 32bits/channel. Before you can apply any photoshop manipulation you need to do tone mapping. Photoshop CS5 has four major options for that:

- Local adaptation
- Equalize histogram
- Exposure and Gamma
- Highlight Compression

My favorite is local adaption.  When this has been applied the image will be converted to a 16-bit representation. I have tested other programs, like Photomatix and Autopano Pro (which can also handle HDR) but found that Photoshop HDR works best for me. The other programs also have issues color space. In HDR you really need to have raw conversion done in the HDR program and I prefer to use a raw converter I know.

After tone-mapping I usually go back to Lightroom as I'm much more comfortable with LR controls than with Photoshop's. That's just a matter of taste or preferences.

The image below is an example of HDR I have done. What I really like is the nice separation in clouds. This is actually one of the HDR images I'm quite satisfied with. My experience is that I could achieve about the same effect by using an image correctly exposed for highlights and use "fill light" in Lightroom to improve shadow detail and apply clarity locally to the clouds.

Regarding DR, it is not my opinion that 7-8 stops of DR is ample, more that 7-8 stops of DR is available in print. In order to fit a large DR in a print you either need to make local manipulations or tone mapping. When you work with shadow/highlight you essentially do tone mapping.

I normally use +/- 2 EV brackets with three exposures. That would give a DR (based on DxO-mark) of around 16 stops on my camera (Sony Alpha). More exposures may be better, of course, but this is what I can achieve comfortably without touching the camera

Best regards
Erik

Erik,
All the more reason to have a camera with a high DR, to reduce the number of occasions when you might see a need to bracket exposures in order to merge to HDR.

Being aware of a need to bracket exposures in order to increase DR is one thing. Being able to do that successfully is another thing. First, the scene really does have to be stationary. I've bracketed exposures of the Himalayas with camera on tripod, only to discover back home that the very slight breeze causing movement of the tall grass in the foreground, and the slight movement of the distant clouds in the background, has made the merging to HDR process too difficult to bother with.

In such circumstances I choose the exposure which is closest to an ETTR and do my best to cover up any noise which might be apparent in the shadows.

Having successfully merged different exposures to HDR without any 'misalignment' of detail, there's sometimes a further problem of making the right 'tone-mapping' adjustments to get the image looking natural.

In my view, this is partly because one is faced with a whole new system of tonal adjustments which are different from the regular adjustments in ACR that one might be familiar with.

Another issue is the number of auto-bracked shots the camera is capable of. I've often found with Canon cameras that the maximum of +/- 2EV with just 3 shots is not ideal for merging to HDR. The extension of 4 stops of DR may be sufficient, but the gap of 2EV between each exposure may not produce in the best result. 5 frames with a 1EV difference between shots would be better.


I've noticed, Erik, that you've mentioned this factor before, quite frequently, implying that in some way the DR limitations of the print medium makes a high DR capability in the camera irrelevant or less relevant.

This is simply not true if one knows how to process an image in Photoshop. It's possible to display, in a natural way, the full dynamic range on the print of any correctly exposed high-SBR scene, even if the scene encompasses a whopping 20 stops of DR.

How is this possible? First, let me explain how the eye perceives a scene. (In simple terms so I can understand it myself).

The eye has a surprisingly narrow field of view as regards discernment of detail. Peripheral vision tends to give us the impression that the eye's FoV is quite wide, but peripheral vision is mainly good for the detection of movement. It's totally hopeless for the discernment of detail. To see all the detail in a scene that may be captured even by a moderately wide-angle lens, we have to shift our gaze from side to side, the equivalent of image stitching in a camera.

A similar situation applies to the eye's DR capability. When perusing a scene, we find in one moment we can see lots of detail in the white, fluffy clouds in the sky, then a fraction of a second later, as we shift our gaze to some shadows at the foot of a nearby tree, we can see leaf litter and lots of fine detail in the dark shade which really doesn't look all that dark anyway, but would look very dark if we were to photograph the scene with a single shot, exposing for the clouds.

It's easy to get the impression that the eye has a very wide DR capability. In a sense, it does, but only because it has the capability of bracketing exposures. The pupil of the eye, which is similar to the aperture of a camera lens, can dilate and contract in a fraction of a second in order to accommodate changing brightness levels.

Sometimes, when the change in brightness is extreme, it may take several seconds for the eye to adjust, such as coming out of a darkened cinema into the bright sunlight. But normally, a shift in brightness of just a few stops is almost instantly accommodated by a change in the aperture of the pupil.

So basically, if we compare the eye with a camera, using camera terminology, the eye is continually performing image stitching to widen its FoV, and continually bracketing exposures in order to increase its dynamic range.

A single shot from a camera, any camera, even the D7000, cannot compete with the eye as it's normally used with its continual gaze-shifting and changes of aperture.

Okay! All that must be crystal clear to you all, so let's move on to the print. How do we portray on a print, with its very limited DR, the full DR of a 20 EV scene?

Well, I'm no expert on the potential of the myriad of processes and techniques in Photoshop. I'm sure Jeff Schewe could make me look like a complete novice in that respect.

But there are a few very simple techniques that work quite well for me. First, the Shadows/Highlight tool. You need to be in advanced mode of course, but this is a tremendously useful feature in Photoshop for quick adjustments of balance between shadows and highlights. If you need more extreme adjustments, you can repeat the process.

Another simple technique (you must have noticed, I like simplicity), is to select with the lasso tool any area on the image you want to treat separately, feather appropriately (30, 50 or 100 pixels), then apply whatever adjustments you think appropriate.

By such processes, you can achieve on the print, the full detail of a bright cloud in the sky, and the full detail in the shadows at the foot of a tree in the foreground, if your camera has sufficient DR or, if you bracket exposures and merged to HDR.


.

You are confusing the 'subjective' with the 'objective' here. The term, 'better', without a qualifying description, is about as subjective as one can possibly get. However, 'less noise' is a comparative matter which is either true or false. If it is determined to be true, objectively, through the sorts of measurements that DXO make, but subjectively one cannot see it, then one can reasonably surmise a number of possible causes.

(1) One doesn't know what 'visual' noise is and therefore cannot recognise it.

(2) The differences in noise are so small that they are irrelevant in practice, or beyond the threshold of normal discernment.

(3) The display medium, monitor or print, is not of sufficient quality, or not sufficiently well-calibrated, to enable the observation of such differences.

(4) The observer has a medical or genetic problem with his eyesight.

Of course, there may be other reasons of a more psychological nature, which perhaps we should not dwell upon. People can have 'blind spots'. Sometimes seeing the truth is too painful, so we bury our head in the sand.

Sometimes people identify so strongly with their camera equipment that it becomes part of their personality, so any criticism of their camera equipment is viewed as a criticism of themselves, their taste and their judgement.

So, if camera A has better high-ISO performance than camera B, then someone who owns camera B, of which he is very proud and which symbolizes his good taste and discernment, may first try to dispute the validity of the tests that imply that camera A has better ISO performance.

Having failed to convincingly win the argument that the tests are invalid or inaccurate, because of mounting photographic evidence that camera A really does have better high-ISO performance than camera B, the owner of camera B may then resort to other tactics to preserve his self-esteem.

A typical response might be, "I never use high ISO, so it's irrelevant." Or, in the case of camera A having a wider DR than camera B, "I'm not interested in pixel-peeping shadows. The DR of my current camera B is quite sufficient."

One sees many examples of such attitudes on DPreview.

By the way, Erik, your example images of HDR do not appear in IE when I click on them. There's something wrong.

Cheers!
Title: Re: Nikon D7000 Dynamic Range
Post by: Bart_van_der_Wolf on November 27, 2010, 06:24:39 am
The image below is an example of HDR I have done. What I really like is the nice separation in clouds. This is actually one of the HDR images I'm quite satisfied with. My experience is that I could achieve about the same effect by using an image correctly exposed for highlights and use "fill light" in Lightroom to improve shadow detail and apply clarity locally to the clouds.

Hi Erik,

That's a nice image. The whole issue with HDR is more to do with the inability of a complete camera system to capture the scene dynamic range in a single shot. The sensor may be able to capture, say, 11 stops of range, but the lower exposed regions do not carry enough useful data to exploit in postprocessing. What's more, the lens will further severely limit the useful dynamic range of the sensor, maybe to 9 stops.

HDR allows to break free from these physical limitations. By offering better S/N ratio throughout the dynamic range, we get an enormous potential of tonality manipulation, without the noise compromises. As an example of what creative potential lies hidden in even a JPEG like the one you just posted (admittedly already tonemapped), I've attached a modified version of it (If you don't like me doing that without your permission, I''ll remove it, let me know). It's not necessarily better, because that depends on your preferences. All I wanted to show is that with the proper tools, one can exploit the potential in an image file better, and the more potential, the more options we have.

Cheers,
Bart

P.S. I used SNS-HDR for the tonemapping with the JPEG file as a source. It's just one of a myrad of possible renditions.
Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on November 27, 2010, 08:13:09 am
Hi Bart,

I don't disagree with you view. It's just that my experience is that DSLRs have ample range. Might be that my brain is still influenced me shooting Velvia on MF.

I appreciate your effort rendering my image. The original DNG files are here: http://echophoto.dnsalias.net/ekr/images/ToBart/

Best regards
Erik

Hi Erik,

That's a nice image. The whole issue with HDR is more to do with the inability of a complete camera system to capture the scene dynamic range in a single shot. The sensor may be able to capture, say, 11 stops of range, but the lower exposed regions do not carry enough useful data to exploit in postprocessing. What's more, the lens will further severely limit the useful dynamic range of the sensor, maybe to 9 stops.

HDR allows to break free from these physical limitations. By offering better S/N ratio throughout the dynamic range, we get an enormous potential of tonality manipulation, without the noise compromises. As an example of what creative potential lies hidden in even a JPEG like the one you just posted (admittedly already tonemapped), I've attached a modified version of it (If you don't like me doing that without your permission, I''ll remove it, let me know). It's not necessarily better, because that depends on your preferences. All I wanted to show is that with the proper tools, one can exploit the potential in an image file better, and the more potential, the more options we have.

Cheers,
Bart

P.S. I used SNS-HDR for the tonemapping with the JPEG file as a source. It's just one of a myrad of possible renditions.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 28, 2010, 04:53:30 am
I don't disagree with you view. It's just that my experience is that DSLRs have ample range. Might be that my brain is still influenced me shooting Velvia on MF.

That's a nice image, Erik, that you can be proud of. When I first saw it, I attempted to brighten the tonality of the large rock on the right, similar to what Bart has done, but it was late at night and I needed some sleep.

Which DSLR are you referring to, Erik?

If you are referring to the 24mp Sony A900 which has a very respectable DR at base ISO, more than a stop better than my 12mp Canon 5D at normalised print sizes, then I can understand why you may be quite satisfied with the relative lack of noise in the shadows, especially if you print no larger than A2.

My situation is quite different. My full frame cameras (the 5D and D700) are only 12mp, but my printer is a 24" wide format. If I wish to make a 24"x 36"print from a 5D or D700 file, then the detail and noise I see at approximately 80% on my 24" 1920x1080 LCD monitor, is what I get on a 24"x36"print at a ppi of 240.

However, if you are making an  A2 size print, say 400mm wide in portrait mode, then you should be viewing 'print' size on an HD monitor at approximately 36% enlargement (assuming you're viewing a file of 256ppi on a 24" HD monitor. At 240ppi you would get a 17" wide print, portrait mode.).

At such reduced enlargement, noise and lack of detail in the shadows is less of a problem.

I've taken more images with my 5D, since I bought it in November 2005, than with any other camera in my entire life.  Because I frequently use the camera without a tripod, often with little time to take accurate spot meter readings for ETTR purposes, I often bracket exposure, but not for the purpose of merging to HDR, but to make sure I get an exposure which is reasonably close to an ETTR.

Such bracketing may be +/- 2/3rds of a stop, and sometimes +/- 1 stop. Sometimes, I've bracketed hand held shots for merging to HDR. Then the difference in exposure between the lightest and the darkest is usually 4 stops. But hand-held shots tend to be 'hit & miss' when merging to HDR. I'd prefer to use a tripod.

The fact is, I have hundreds of pairs of shots that differ in exposure between the lightest and darkest by 2 stops, and where the darkest shot is an ETTR. The difference in noise and detail in between the lightest and darkest, not only in the deep shadows, but also in the lower mid-tones, is very obvious at 80% on my monitor, and even more obvious at 100% of course.

I tried doubling the files size of a noisy 5D shot, then viewing it at 36% on my monitor. The shadow noise was noticeably reduced. I can well imagine if the 5D had the same DR specs as the A900 at base ISO, then at A2 print size, I would be less concerned with DR issues.

However, the D7000 at base ISO and normalised print sizes, say up to 14"x21"at 240ppi, has a significant 1 & 1/2 stops higher DR rating than the A900, although it should be said that the DR advantage gradually reduces at higher ISOs so that at ISO 1600 the DR of the D7000 is only 2/3rds of a stop better, and at ISO 3200 only 1/2 a stop better.

All the other parameters, SNR, tonality and color sensitivity seem to be about the same at all ISOs, for the A900 and D7000.

I've done such a fantastic job of promoting this camera to myself, I'm unable to resist placing an order for one. I expect to receive it some time next week. I've also placed an order for the Nikkor 24-120/F4 VR which effectively doubles the cost.

The question is, '"Will I, or will I not, see the following 2-stop difference in shadows and lower mid-tones, when I compare the new camera with my old Canon 5D (old but full frame)?"
One of these 100% cropss is from an ETTR at ISO 100, F11 and 1/200th sec. The other is at the same ISO and F stop, but overexposed by 2 stops, ie 50th sec. No prizes for guessing which is which.  ;D
Title: Re: Nikon D7000 Dynamic Range
Post by: ejmartin on November 28, 2010, 12:51:18 pm
Honestly, I would enjoy having an effectively "ISO-less" camera such as the D7000.  The ISO control is for me a nuisance, a workaround for the suboptimal capture chain electronics of my Canon DSLRs.  It is of course not strictly speaking an "exposure" control, it is a "rendering" control; so why not leave it to the time when I want to render the image rather than capture it?  The camera's meter should be able to suggest a rendering intent and use it for jpeg creation, but leave the amplification setting as metadata rather than a hardware amplification that throws away image data.  Being able to capture at close to base ISO and set exposure compensation in post would enable me to concentrate on the actual exposure parameters of aperture and shutter speed and not have to worry about whether the camera electronics is getting in the way of optimal capture for those exposure settings.
Title: Re: Nikon D7000 Dynamic Range
Post by: Roy on November 28, 2010, 06:21:54 pm

Another pertinent question would be, ''What proportion of photons arriving at the outer surface of the sensor is blocked or absorbed by the various filters before the light even reaches the photodiode?

We know that the Color Array Filter of the Bayer-type sensor absorbs at least half of the light reaching it. The green filter has to exclude both red and blue frequencies, otherwise the pixel wouldn't be green. Furthermore, it is reasonable to assume that other filters such as the AA filter, IR filter and even the slight degree of opacity of the microlenses and filters will absorb yet more light.

Such facts seem significant to me because shot noise is caused by the slightly random and unpredictable arrival of individual photons during any given exposure of the sensor. Such shot noise exists before the photons pass through the various absorbing filters and microlenses. It therefore seems reasonable that the calculations for shot noise (the square root of the mean average of photons collected by the photodiodes) should in fact be applied to the number of photons arriving at the sensor's outer surface. Would you agree or not?

If this is the case (and I'm certainly not asserting that it is), we cannot use the 'electron charge' figure for calculations regarding shot noise.

Consider a situation where the full-well capacity of the D7000 is, for argument's sake, 32,768 e-. The 11th stop down from (and including) full-well capacity should then have a charge of just 32 e-. But that does not necessarily mean that the shot noise is sqrt of 32, or 5.65 photons which represents about 17% of the signal, which is quite high, but in fact may be the sqrt of 100 photons which represents a shot noise of just 10%.

Would you agree? If not, please enlighten me.

Hi Ray,

The quote above is equivalent to saying that the shot noise of a constant light source when attenuated by absorption no longer has a Poisson distribution. If it was true, the light on a dark cloudy day would record with no more noise that on a bright sunny day, and deep shadows in a room illuminated by a narrow beam of bright sunlight would be noise-free. This is about discrete quantized events which do not scale in a linear fashion. To take another example, if we toss a coin many times and look at the variation of outcomes of only a random 10% of the tosses, your argument would predict that the variation of the 10% sample would, on average, equal the variation of the total outcomes. Clearly not so.

Another observation: note that the standard deviation of photon noise is only equal to the square root of the number of photons for large numbers of photons. For large numbers the Poisson distribution approaches the normal distribution which has the simple square root relationship. 5.65 is not a large number.

Cheers
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 28, 2010, 10:17:44 pm
Honestly, I would enjoy having an effectively "ISO-less" camera such as the D7000.  The ISO control is for me a nuisance, a workaround for the suboptimal capture chain electronics of my Canon DSLRs.  It is of course not strictly speaking an "exposure" control, it is a "rendering" control; so why not leave it to the time when I want to render the image rather than capture it?  The camera's meter should be able to suggest a rendering intent and use it for jpeg creation, but leave the amplification setting as metadata rather than a hardware amplification that throws away image data.  Being able to capture at close to base ISO and set exposure compensation in post would enable me to concentrate on the actual exposure parameters of aperture and shutter speed and not have to worry about whether the camera electronics is getting in the way of optimal capture for those exposure settings.

Emil,
I agree completely. If one is concerned about subtleties of image quality, smoothness of tonality, noise in the shadows etc, then it follows one would also be concerned about getting an ETTR exposure at the appropriate ISO. With Canon DSLRs this involves the dual concern about avoiding overexposure which will blow out the highlights, and underexposure which will increase noise in the mid-tones, lower mid-tones and shadows.

With the D7000 it seems one might have only the one concern regarding correct exposure, and that is to avoid overexposing at base ISO, (having of course already chosen an appropriate shutter speed and aperture for the circumstances).
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 28, 2010, 10:31:14 pm
Hi Ray,

The quote above is equivalent to saying that the shot noise of a constant light source when attenuated by absorption no longer has a Poisson distribution. If it was true, the light on a dark cloudy day would record with no more noise that on a bright sunny day, and deep shadows in a room illuminated by a narrow beam of bright sunlight would be noise-free. This is about discrete quantized events which do not scale in a linear fashion. To take another example, if we toss a coin many times and look at the variation of outcomes of only a random 10% of the tosses, your argument would predict that the variation of the 10% sample would, on average, equal the variation of the total outcomes. Clearly not so.

Another observation: note that the standard deviation of photon noise is only equal to the square root of the number of photons for large numbers of photons. For large numbers the Poisson distribution approaches the normal distribution which has the simple square root relationship. 5.65 is not a large number.

Cheers


Hi Roy,
I'm not sure I understand your explanation. I'm working from the principle that the shot noise is proportional to the sqrt of the total number of photons that pass through the shutter.
According to this principle, the shot noise in a photo taken on a cloudy day should be less, as a proportion of the total signal, than the shot noise in the same scene taken on a sunny day, assuming appropriate ETTR exposures in each case.

Whether the sun shines or not, the full-well capacity of the camera remains unchanged. The exposure should be greater for the cloudy-day shot in order to achieve a full-well charge in at least some of the pixels.

Because the contrast and brightness range in the scene on a cloudy day is less, a greater proportion of the pixels will achieve the maximum full-well charge, and a greater proportion will achieve 3/4 potential charge, and 1/2 potential charge, and so on.

The shot on the sunny day, on the other hand, will have more shadows and deeper shadows where the signal is dominated by shot noise in the parts of the sensor recording the signal..

The total number of photons passing through the shutter, in the shot on the cloudy day, will be significantly greater, and whilst the shot noise in an absolute sense will also be greater, it will be significantly less as a proportion of the over all signal.

Let me rephrase the question because this is really outside my area of expertise, and I'm not at all sure I'm right.

Consider two hypothetical cameras. Camera A has a perfect quantum efficiency at the photodiode level and amazing transparency of all its filters and microlenses which absorb no light whatsoever. It's the mythical perfect camera.

Let's suppose that the electron charge in the 11th stop down from full-well capacity is a mean average of 32e- and that this charge has been achieved by a certain number of photons exiting the lens and passing unhindered through the open shutter to the photodiodes where they knock off, on average, 32 electrons from the silicon substrate of each diode, one photon per electron.

Let's now consider Camera B with the same number of pixels with the same full-well capacity. The difference is that Camera B has a fairly low quantum efficiency and a lot of slightly opaque filters and microlenses, including one very opaque filter, the Bayer Color Filter Array.

Let's suppose that in order to achieve that average charge of 32e- in each pixel in the 11th stop in Camera B, we need to let in 8x the amount of light. Instead of an average of 32 photons per pixel, we need an average of 256 photons per pixel. Instead of an exposure of 1/200th at F11 for camera A, we need an exposure of 1/25th at F11 for Camera B.

Now, it seems reasonable to me, in my ignorance, to surmise or deduce that Camera B will exhibit less shot noise in the RAW file, than Camera A, although Camera A, being a mythically perfect camera, will possibly have lower noise in total because the only noise it will produce (or reproduce) is shot noise.

Camera B on the other hand will likely produce images with noise which is predominantly read noise, thermal noise, fixed pattern noise and the whole gamut of various noise types. Its lower shot noise (in proportion to signal) will not help much in these circumstances.

You might be right, but I'm not convinced yet  :)  .

Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on November 28, 2010, 11:54:33 pm
Ray,

My first experiments with HDR were on my Alpha 100. That camera had less DR than what I have to day. HDR programs were less well developed at that time. So I tested HDR and did not like the results.

Regarding your D7000, I just hope that you see the advantages you expect! Please share the experience.

I normally don't print that large. A2 is my standard size, anything larger is printed on Durst Lambda at a pro lab. I never did any large print from images having excessive dynamic range, so I have not that experience.

Best regards
Erik


Which DSLR are you referring to, Erik?


The question is, '"Will I, or will I not, see the following 2-stop difference in shadows and lower mid-tones, when I compare the new camera with my old Canon 5D (old but full frame)?"

Title: Re: Nikon D7000 Dynamic Range
Post by: PierreVandevenne on November 29, 2010, 03:59:18 pm
Let's suppose that in order to achieve that average charge of 32e- in each pixel in the 11th stop in Camera B, we need to let in 8x the amount of light. Instead of an average of 32 photons per pixel, we need an average of 256 photons per pixel. Instead of an exposure of 1/200th at F11 for camera A, we need an exposure of 1/25th at F11 for Camera B.

Now, it seems reasonable to me, in my ignorance, to surmise or deduce that Camera B will exhibit less shot noise in the RAW file, than Camera A, although Camera A, being a mythically perfect camera, will possibly have lower noise in total because the only noise it will produce (or reproduce) is shot noise.

Camera B on the other hand will likely produce images with noise which is predominantly read noise, thermal noise, fixed pattern noise and the whole gamut of various noise types. Its lower shot noise (in proportion to signal) will not help much in these circumstances.

You might be right, but I'm not convinced yet  :)  .


If you push your example to the extreme, you'll see that a camera with 0.001% effective QE would be even better than your camera B.

Try to look at "shot noise" it from the side of received/measured/counted photons.




Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 29, 2010, 07:57:49 pm
If you push your example to the extreme, you'll see that a camera with 0.001% effective QE would be even better than your camera B.

Hi Pierre,
My point is not that Camera B is better than Camera A, but that the signal in Camera B contains a lower proportion of shot noise. If the effective QE of Camera B were 0.001% then a normal exposure in bright daylight, at base ISO, might take 10 seconds or more, instead of 1/100th of a second at the same aperture with Camera A.

In such a situation, it seems to me, that shot noise in Camera B would become totally irrelevant, and noise from sources other than readout noise would increase, such as thermal noise.

Quote
Try to look at "shot noise" it from the side of received/measured/counted photons.

Okay! I'll try. But I'm not Einstein and it's very difficult. I have virtually no understanding of why the processing of received light, once it has entered the camera and the shutter has closed, should increase the proportion of shot noise in the final signal, expressed as an electron voltage.

This is how I imagine the shot noise occurs. For the sake of simplicity, let's imagine we have a shutter than opens and closes intantly, faster than the speed of light, and that the entire signal for the entire scene exists momentarily inside the camera body, before it gets processed, and before it passes through the various obstacles on its way to the photodiodes.

Let's quantify the number of photons in that entire signal as being 1 million, for the sake of simplicity. The shot noise should be sqrt of 1 million = 1,000 photons, or 0.1% of the total signal. If that's true, then it's an insignificant amount of noise. Right?

Let's now consider the effects of just one aspect in the processing chain, but the real 'bady', the Color Filter Array which absorbs about half the light that has entered the camera.

In one fell swoop we are suddenly reduced to 500,000 photons. The other 500,000 have got absorbed by the CFA.

Now you (and Roy) seem to be implying that the CFA has a bias towards 'misbehaved, naughty' photons (those that arrived early or late), and lets pass a greater proportion of the 'naughty' photons.

If that's the case, please explain why. The shot noise in a million photons is 0.1% of the signal, whereas the shot noise in 500,000 photons is 0.14%. Why the bias towards 'noisy', 'misbehaved' photons?

Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 29, 2010, 08:28:30 pm
Regarding your D7000, I just hope that you see the advantages you expect! Please share the experience.

Thanks Erik. Will try to do. I'm very curious as to why some people give little or no credence to the DXO results.

I tend to think the reasons are either due to personal bias or a lack of understanding of the meaning of the graphs and the differences between the normalised print results and the 'screen' results. The graphs are quite explicit and very accurate in my opinion.

I find it quite uncanny that a year or more before DXO published its test results, I had already determined that the maximum DR of my Canon 5D, from the perspective of discernment any detail, however degraded, was in the order of 11 to 12 stops, depending on the accuracy of the ETTR exposure in the first stop, which I assess by a 2/3rds of a stop negative EC adjustment in ACR, but which the late Gabor (Panopeeper) assessed slightly differently. He reckoned my ETTR exposure was in fact slightly clipped.

DXOMark describe the DR of the Canon 5D as being 11.13 EV. Here are my test results, from about 2 years ago, using Jonathan Wienke's DR Test Target (thanks Jonathan! ).
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 29, 2010, 08:33:49 pm
The image of the 12th stop doesn't show on my browser.

I'll try again.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 29, 2010, 08:39:33 pm
Oops! Looks like all that noise is producing a larger jpeg. Here's a downsized image.

Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on November 29, 2010, 09:17:52 pm
Ray,

I don't know. In my view the data is both interesting and useful. Two issues I may have are:

Don't really like bunching all data in one figure of merit.

The DR measurement is feasible but not very relevant due to the definition used. Nothing wrong with the definition, but it may be less relevant to photography.

I got a mail from Mark Dubovoy, who sometimes seem to be critical of DxO data, saying that the data itself is excellent but is used incorrectly by many posters. This may also be my opinion.

There is a wealth of data in those measurements!

Regarding DR, it has seldom been a problem for me, but I will revisit the issue, and also check with Jonathan's test targets.

Best regards
Erik


Thanks Erik. Will try to do. I'm very curious as to why some people give little or no credence to the DXO results.

Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 29, 2010, 09:22:48 pm
For those who are interested, here's the 10th stop (that's 10 stops including the first stop). I think you will agree that this quality could be useful for espionage purposes, determining car number plates in the dark for example.

The big question for me is, will the D7000 be able to turn such an exposure into a photographically useful part of an image in the shadows.

In true Aussie fashion, I'm now taking bets on this issue. I can receive betting payments through PayPal, and to check out the odds I'm offering, visit my website at......... just joking!  :D ;D :D .
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 29, 2010, 09:45:38 pm
Regarding DR, it has seldom been a problem for me, but I will revisit the issue, and also check with Jonathan's test targets.

Erik,
It has seldom been a problem for you because you instinctively avoid photographing scenes which you know will not turn out well, considering the DR limitations of the camera. An extreme example, but also relevant for less extreme situations, is the shot of a scene out of a living room window, offering a view of lovely clouds, perhaps a river view, or even a view of the Himalayas.

Without fill-flash, which tends to produce unnatural black shadows unless one has expertly arranged the lighting as a professional might with his truck-load of gear, one ends up with a beautifully exposed view through the window, but the interior of the living room, which might be quite stylish and deserve attention in its own right, is totally and unacceptably noisy.

In such extreme situations, even the D7000 will be found to be lacking, and bracketing exposure is the only solution. But for less extreme situations, the D7000 might do the job without the need for bracketing.

That's the point I'm trying to get across.
Title: Re: Nikon D7000 Dynamic Range
Post by: PierreVandevenne on November 29, 2010, 10:15:05 pm
Now you (and Roy) seem to be implying that the CFA has a bias towards 'misbehaved, naughty' photons (those that arrived early or late), and lets pass a greater proportion of the 'naughty' photons.
No, not really. Essentially, and in this case, you are sampling the signal. There are no naughty photons, no well behaved photons.
If the average stream of measured photons is 1 per exposure, there is a 36.8% chance that your exposure will record nothing, a 36.8% chance that it will record 1 photon, 18.4% it will detect 2, 6.1% that it will detect 3, 1.5% that it will detect 4, etc... If the average stream is 10 per exposure, you'll get 9 / 10 in 12.5% of the cases, more than 11% for 8 / 11, around 10% for 12, apporx 9.5% for 7 etc... (the Poisson distribution is a bit skewed but tends to become quite close to a Gaussian distribution after 20-30 samples). It's not how many photons there were in the first place that matter (if that was the case, there would be close to zero noise in the shot of the light from a distant star eventhough the light was filtered by light years of dust, the atmosphere, etc...) but what we sample out of the photon stream. Saying "here's the shot noise" is saying "there's the uncertainty on the signal we measure". The more individual events in the sample, the closer it will statistically be from the average stream, which we consider the "real value". To go back to the coins example, the 100 toss sample will be on average closer to 50-50 than two individual 10 samples. The 500000 photons at the diaphragm are not your sample, they 150.000 at the sensor are.
Now, for the funny aspect of the issue, if our perceptions were extremely fast samples of the physical world, much faster than the speed at which photons arrive (obviously impossible but still fun to think about it), a shot with 0 photon could be the way I see and remember a scene - my reality - and the same shot with 2 photons could be the way you see and remember it - a different reality...
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 30, 2010, 06:16:20 am
No, not really. Essentially, and in this case, you are sampling the signal. There are no naughty photons, no well behaved photons.

Of course. I realise this. I was speaking metaphorically and being a bit facetious.  :D

As I understand this issue of shot noise, in layman's terminology since I'm clearly not a quantum physicist, in any given exposure of a supposed constant light source (say a star as viewed from the atmosphere-free moon), the number of photons that pass through the open shutter of a camera will vary with each exposure, despite everything else (f stop and shutter speed etc) being the same.

Just like tossing a coin will produce a result close to 50% heads and 50% tales after many events, the more exposures we take, the closer the variation in photon count will be to the sqrt of the average number of photons in each exposure. Is this correct?

One interesting feature of Photoshop Extended is the facility to stack a number of images and get one resulting image which consists of the best exposed pixels from each of the stacked images. I haven't pushed this to its limits yet, due to lack of computer power. My experiments as I recall, when I first got CS3E, have consisted of about 6 stacked  images.

The improvement in noise with just 6 images was quite dramatic. I would describe it as a 2 stop difference at high ISO. In other words, 6 stacked images at ISO 3200 after processing, look as clean and sharp as a single shot taken at ISO 800.

Now at high ISO shot noise will be greater, but also SNR in general will be worse.

I have no idea to what extent this 2-stop improvement is due to countering the effects of shot noise, or due to countering the random effects of normal signal processing. Perhaps you can tell me.
   
Quote
If the average stream of measured photons is 1 per exposure, there is a 36.8% chance that your exposure will record nothing, a 36.8% chance that it will record 1 photon, 18.4% it will detect 2, 6.1% that it will detect 3, 1.5% that it will detect 4, etc...

If you had a perfect Bayer type Color Filter Array in which the red filter was perfectly transparent to photons of the red wave length, and perfectly opaque to photons in the green part of the spectrum, a single photon of red wave length, after passing through the shutter, would stand only a 25% chance of getting through the CFA, for a start.

With a 'real-world 'CFA in a 'real-world' camera, the chances would be considerably less than 25%, and the chances of that photon knocking an electron off the silicon substrate of the photodiode, would be yet again less, in my humble opinion. I'd give it no chance.  ;D
Title: Re: Nikon D7000 Dynamic Range
Post by: hjulenissen on November 30, 2010, 06:34:48 am
DXOMark describe the DR of the Canon 5D as being 11.13 EV. Here are my test results, from about 2 years ago, using Jonathan Wienke's DR Test Target (thanks Jonathan! ).
Thank you.

What do you think about this way of measuring DR for highly nonlinear devices, i.e. film? It seems to me that if 20 stops of dynamic range is captured (using e.g. HDR), representing that in a globally tonemapped 8-bit jpeg file as "20 stops of DR" is somewhat misleading, even if some details can be discerned that far apart?

-h
Title: Re: Nikon D7000 Dynamic Range
Post by: PierreVandevenne on November 30, 2010, 07:18:28 am
source (say a star as viewed from the atmosphere-free moon), the number of photons that pass through the open shutter of a camera will vary with each exposure, despite everything else (f stop and shutter speed etc) being the same.

Just like tossing a coin will produce a result close to 50% heads and 50% tales after many events, the more exposures we take, the closer the variation in photon count will be to the sqrt of the average number of photons in each exposure. Is this correct?

On the whole that is the idea.

[quote}
One interesting feature of Photoshop Extended is the facility to stack a number of images and get one resulting image which consists of the best exposed pixels from each of the stacked images. I haven't pushed this to its limits yet, due to lack of computer power. My experiments as I recall, when I first got CS3E, have consisted of about 6 stacked  images.

The improvement in noise with just 6 images was quite dramatic. I would describe it as a 2 stop difference at high ISO. In other words, 6 stacked images at ISO 3200 after processing, look as clean and sharp as a single shot taken at ISO 800.

Now at high ISO shot noise will be greater, but also SNR in general will be worse.

I have no idea to what extent this 2-stop improvement is due to countering the effects of shot noise, or due to countering the random effects of normal signal processing. Perhaps you can tell me.
 [/quote]

Again roughly speaking, stacking images improves the number of photons collected and therefore increases the S/N ratio. If you want to improve the signal to noise ratio by a factor of 4, you need 16 exposures. Assuming your exposure period doesn't overflow your electron bins, a single exposure equivalent to the total exposure of the stacked exposure should have a bit less noise than the stack because the individual components of the stack each suffer from read noise.

In practice, there are many sources of noise that should be considered.

For example, if you have a camera with a very low read noise,  stacks won't lose that much quality compared to a single equivalent exposure. If you have a sensor that overheats easily, a stack of short exposures is likely to be better than a single longer exposure because it will suffer less from dark current. etc... etc...

The rule of thumb for amateur astronomy for example is to use the camera at its "optimal ISO" and collect as much photons as possible. That's basically attemtpting to obtain the ISO-less camera ejmartin wants.
Title: Re: Nikon D7000 Dynamic Range
Post by: bjanes on November 30, 2010, 09:22:53 am
The image of the 12th stop doesn't show on my browser.

I'll try again.

Ray,

Your image has strong pattern noise in the deep shadows, typical for many older Canon's. If you read Emil Martinec's (http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/index.html) excellent treatise on noise and dynamic range, he classifies that as one type of PRNU (pixel response non-uniformity). Such pattern noise has a more detrimental effect on image quality than a mere standard deviation would indicate. BTW, it is typically greater for CMOS than CCD, since the former has an amplifier for each pixel.

Furthermore, such noise would not be included in the engineering definition of DR, since full well (in electrons) and read noise are determined by subtracting duplicate frames to eliminate fixed pattern noise (see Roger Clark (http://www.clarkvision.com/imagedetail/evaluation-1d2/index.html)).

DXO does not describe their DR measurement in detail, but they use a circular array of neutral density optical filters somewhat analogous to the use of a Stouffer wedge (where the steps are arranged in a linear fashion). DR is taken as the maximum signal divided by the step where the SNR (signal to noise ratio is unity). This would include pattern noise and veiling flare.

If readers think that this DR is too liberal, one can use the expanded DXO SNR graphs as explained by Emil (http://www.luminous-landscape.com/forum/index.php?topic=42158.0).

Regards,

Bill
Title: shot noise depends on number of photons detected
Post by: BJL on November 30, 2010, 03:30:55 pm
Ray,

    given your offensive and irrelevant accusations about my opinion of DXo, I probably should not bother to reply at all. After all, my comments carefully avoided any judgement on the accuracy of DXo's measurement: my main point n recent posts is simply that your possible evidence of dark noise affecting IQ with one camera (the 20D) is irrelevant to whether dark noise can significantly effect IQ in another camera with far less dark noise (the D7000).

But I am replying to help you with a factual misunderstanding: shot noise depends on the number of photons detected, and is roughly the square root of the number detected, limiting SNR to the square rot of the number of photons detected. So as long as your hypothetical less sensitive camera B is using a higher exposure level (longer exposure time and or lower f-stop) and so receiving more photons in order to detect the same number of photons, and produce the same number photo-electrons, it will have the same shot noise, not less. Otherwise, ND filters would solve all out shot noise problems when long enough exposures can be used!

For the same reason, a lower light level (cloudy day) does not reduce the effect of shot noise on IQ in any useful way: in reducing both signal and shot noise, less light received/detected gives a worse ratio of signal to shot noise, along with a worse still ratio of signal to dark noise, and so an overall worse ratio of signal to noise.

Hopefully I can leave it to to real experts like Bill Janes and Emil Martinec from here in.
Title: Re: shot noise depends on number of photons detected
Post by: bjanes on November 30, 2010, 05:40:06 pm

Hopefully I can leave it to to real experts like Bill Janes and Emil Martinec from here in.

BJL,

Thanks for the compliment, but I am hardly in the same league as Emil, who is a real scientist (professor of physics at a major research university). I am merely a medical doctor (pathology and internal medicine) who finds the science of photography to be quite interesting. I find your posts to be very instructive and accurate and would include you as an expert (I gather that your professional background is in engineering).

Regards,

Bill
Title: Re: shot noise depends on number of photons detected
Post by: Ray on November 30, 2010, 06:31:20 pm
Ray,

    given your offensive and irrelevant accusations about my opinion of DXo, I probably should not bother to reply at all. After all, my comments carefully avoided any judgement on the accuracy of DXo's measurement: my main point n recent posts is simply that your possible evidence of dark noise affecting IQ with one camera (the 20D) is irrelevant to whether dark noise can significantly effect IQ in another camera with far less dark noise (the D7000).

Don't be so sensitive, BJL. I was merely using my own test results of the 20D in conjunction with DXO results, in order to predict, or get an impression of, the sort of noise levels I could expect with the D7000. I was also offended by your bringing irrelevant distractions to the issue, such as the 20D being old technology. The age of the 20D does not appear on the DXO graphs, nor on my test images.

I am predicting that the lowest 4 stops within the DR range of the 20D, at base ISO and at the pixel level, will be cleaner in the D7000, and they will be cleaner to the extent which can be observed when those same 4 stops have been captured using the 20D at ISO 1600, with the same exposure.

Quote
But I am replying to help you with a factual misunderstanding: shot noise depends on the number of photons detected, and is roughly the square root of the number detected, limiting SNR to the square rot of the number of photons detected. So as long as your hypothetical less sensitive camera B is using a higher exposure level (longer exposure time and or lower f-stop) and so receiving more photons in order to detect the same number of photons, and produce the same number photo-electrons, it will have the same shot noise, not less. Otherwise, ND filters would solve all out shot noise problems when long enough exposures can be used!

Fair enough! I stand corrected (provisionally). The ND filter is a good analogy, but I don't understand why such increase in exposure to the light before it enters the lens should not reduce the proportion of shot noise in the detected signal to some degree.

However, I can understand why such a reduction in shot noise might never be noticed. If it were possible to reduce shot noise by use of an ND filter and appropriately longer exposure (and I'm certainly not asserting that it is. I'm just trying to wrap my head around this issue), such modest reductions in shot noise would be swamped by the increased 'electronic' noise of the longer exposure required. This is not something that I would know how to test, using my own camera equipment and ND filter. It would be a waste of time trying.

Quote
For the same reason, a lower light level (cloudy day) does not reduce the effect of shot noise on IQ in any useful way: in reducing both signal and shot noise, less light received/detected gives a worse ratio of signal to shot noise, along with a worse still ratio of signal to dark noise, and so an overall worse ratio of signal to noise.

There's a misunderstanding here. I failed to see the relevance of this analogy and merely pointed out to Roy, who made the analogy, that a 'correct' exposure of a scene on a dull day would have less shot noise as a proportion of total signal, than would a 'correct' exposure of the same scene on a sunny day.

Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 30, 2010, 06:59:50 pm
Thank you.

What do you think about this way of measuring DR for highly nonlinear devices, i.e. film? It seems to me that if 20 stops of dynamic range is captured (using e.g. HDR), representing that in a globally tonemapped 8-bit jpeg file as "20 stops of DR" is somewhat misleading, even if some details can be discerned that far apart?

-h

Hi,
I would never attempt to do these sorts of comparisons using film. For a start, you have the DR specifications of the scanner to take into consideration. I've found quite often when scanning film that it has been necessary to make at least two scans, one for the highlights and one for the shadows, and then merge to HDR.

I dont see the compression of a 20 stop DR into an 8 bit jpeg, or onto a print with its 6 or so stops of DR, as being misleading. When the eye peruses a scene with a 20 EV brightness range, it cannot perceive that entire brightness range in one fixed stare, just as it cannot perceive the entire field of view within one fixed stare, excluding peripheral vision. To encompass and register the entire scene in the brain, the eye has to shift its gaze, up and down, or from side to side, and the eyes' pupils dilate and contract according to the brightness of that portion of the scene one is viewing at any specific time.

Compressing the entire DR range into 6 stops on a print allows one to appreciate the whole scene in one glance, unless the print is very large or very wide and one is very close to it.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on November 30, 2010, 07:14:48 pm
Ray,

Your image has strong pattern noise in the deep shadows, typical for many older Canon's.

Don't I know it!  ;D  This pattern noise was the first thing I noticed when I received my 5D about 5 years ago. I thought the camera might be faulty and returned it. The second camera seemed to have slightly less pattern noise in the shadows, so I kept it. But by that time, I had got a clear impression from reports on the internet that this limitation of the 5D was normal.

I recall John Sheehy had a few suggestions of ways to reduce the pattern noise, but I never bothered to explore such techniques. There's a limit to the amount of time I'm prepared to spend in order to extract the Nth degree of detail from an image. I've got far too many images to process and too little time  :D .
Title: Re: Nikon D7000 Dynamic Range
Post by: hjulenissen on December 01, 2010, 02:41:53 am
Hi,
I would never attempt to do these sorts of comparisons using film. For a start, you have the DR specifications of the scanner to take into consideration. I've found quite often when scanning film that it has been necessary to make at least two scans, one for the highlights and one for the shadows, and then merge to HDR.

I dont see the compression of a 20 stop DR into an 8 bit jpeg, or onto a print with its 6 or so stops of DR, as being misleading. When the eye peruses a scene with a 20 EV brightness range, it cannot perceive that entire brightness range in one fixed stare, just as it cannot perceive the entire field of view within one fixed stare, excluding peripheral vision. To encompass and register the entire scene in the brain, the eye has to shift its gaze, up and down, or from side to side, and the eyes' pupils dilate and contract according to the brightness of that portion of the scene one is viewing at any specific time.

Compressing the entire DR range into 6 stops on a print allows one to appreciate the whole scene in one glance, unless the print is very large or very wide and one is very close to it.
That is assuming that the non-linearity is close to the desired one. If it is not, then one will have to apply a new non-linearity to get the desired response. I would guess that one major reason why people wants a large DR is because they assume that this will give them a "large space to work within", extracting and presenting different parts of the tonal range as they see fit.

If the DR is wrapped in a heavily quantized/noisy delivery format, doing significant non-linear adjustement may not be that easy.

"Optimal" tonemapping seems to be closely supported by theory, just like you suggest, yet many photographers are strongly against it. Using whatever nonlinear, non-controllable mapping inherit in analog film seems to be favored amongs many photographers. Why is it so? Only history/habits, or some technical reason that I have missed?

-h
Title: Re: Nikon D7000 Dynamic Range
Post by: BernardLanguillier on December 01, 2010, 06:16:23 am
"Optimal" tonemapping seems to be closely supported by theory, just like you suggest, yet many photographers are strongly against it. Using whatever nonlinear, non-controllable mapping inherit in analog film seems to be favored amongs many photographers. Why is it so? Only history/habits, or some technical reason that I have missed?

It is so because we all do love the security provided by negative films.

In the digital world, we have gotten used to having vivid colors, sharp details,... all the attributes we used to like with slides films together with the impression that we have the DR of negatives... except we don't since a mistake with exposure can be impossible to recover.

Cheers,
Bernard
Title: Re: Nikon D7000 Dynamic Range
Post by: PierreVandevenne on December 01, 2010, 07:28:55 am
Fair enough! I stand corrected (provisionally). The ND filter is a good analogy, but I don't understand why such increase in exposure to the light before it enters the lens should not reduce the proportion of shot noise in the detected signal to some degree.

Get rid of all the photographic analogies the term "shot noise" evokes. The term "shot" here initially came from... a gunshot analogy.
See it as a dry description of the behaviour of the measuring/sampling process.

You can do many intersting things with "shot noise" - that one is, I believe, one of the best teaching experiment on the topic (although it could probably be done with other tools nowadays)

http://www.math.temple.edu/~cmartoff/teaching/ph4796_10/shot_noise/AJP000554.pdf

and even more exotic stuff such as this one

http://europa.agu.org/?view=article&uri=/journals/gl/GL010i001p00005.xml

On a personal basis, I confess that one of the big shocks of my life was to discover that knowing the characteritics of "noise" could yield useful results . Something that I saw as mere measurement pain and trash suddenly became very beautiful.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 02, 2010, 02:02:11 am
Get rid of all the photographic analogies the term "shot noise" evokes. The term "shot" here initially came from... a gunshot analogy.
See it as a dry description of the behaviour of the measuring/sampling process.

You can do many intersting things with "shot noise" - that one is, I believe, one of the best teaching experiment on the topic (although it could probably be done with other tools nowadays)

http://www.math.temple.edu/~cmartoff/teaching/ph4796_10/shot_noise/AJP000554.pdf

and even more exotic stuff such as this one

http://europa.agu.org/?view=article&uri=/journals/gl/GL010i001p00005.xml

On a personal basis, I confess that one of the big shocks of my life was to discover that knowing the characteritics of "noise" could yield useful results . Something that I saw as mere measurement pain and trash suddenly became very beautiful.

Pierre,
Thanks for the links.I'll study them when I have time.

On relfection, I've decided that my speculations on the amount of shot noise existing in the light before it reaches the sensor are philosophically unsound.

We can never be certain about the existence of anything prior to its detection. We can speculate upon its existence and draw inferences about its character, but reality is in the detection.

Therefore I have to concede the point that shot noise cannot exist prior to the detection of the photons. It is nonsense to try to imagine that it might. (Hope I haven't misled anyone  ;) ).

To get back to the purpose of the thread, which was an attempt to find out if the purported increased DR of the D7000 is real and significant, I have now received my D7000 with 24-105/F4 lens, and have made some preliminary comparisons with my 15mp Canon 50D.

The message from some of the more technically-minded members of the forum was that such claimed increases in DR for the D7000, by DXOMark, would be irrelevant because shot noise is already the dominant noise at the extreme end of the DR range in current DSLRs.

The results of my preliminary tests indicate that such a view is incorrect, false, untrue, and plain wrong, to put it mildly.

Of course, I can't speak for the characteristics of every DSLR camera. I can test only the cameras I own. My latest Canon camera is the 50D, and that's the camera the D7000 will replace (at least much of the time).

The Canon D60 might be very marginally better than the 50D in some respects, but so marginally better it's of no significance. For example, the maximum DR of the 50D is 11.4 EV, and the maximum DR of the 60D is 11.5 EV (according to DXOMark). An irrelevant difference.

Comparing the 50D with the D7000, DXO imply in their graphs that the D7000 should have at least similar image quality in the 13th stop as the D50 in the 11th stop. To be precise, the D7000 maximum DR is 13.87 EV and that for the 50D 11.4 EV.

If I ever take the trouble to address this issue more precisely and repeat the test, I'll get some results for the D7000 at 13.67 stops, and for the 50D at 11.33 stops, but for now 13 stops compared with 11 stops should be sufficient for a fair idea.

You should be able to see that the D7000, at 2 stops less exposure than the 50D, actually provides slightly greater detail than the 50D shot at 2 stops more exposure.

This is a remarkable acheivement for Nikon, and a remarkable acheivement for the accuracy and practical relevance of DXO testing procedures.

I'm not going to show you comparisons between the D7000 10th stop and the 50D 10th stop here, but believe me, one is of usable quality and the other ain't.

Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 02, 2010, 02:15:59 am
I've got no idea why this image I've just posted above does not appear in my Win7 Inernet Explorer browser when I try to view it.

What's going on?
Title: Re: Nikon D7000 Dynamic Range
Post by: hjulenissen on December 02, 2010, 04:30:08 am
Google chrome reports it as 0KB when I download it.

-h
Title: Re: Nikon D7000 Dynamic Range
Post by: hjulenissen on December 02, 2010, 04:37:58 am
It is so because we all do love the security provided by negative films.

In the digital world, we have gotten used to having vivid colors, sharp details,... all the attributes we used to like with slides films together with the impression that we have the DR of negatives... except we don't since a mistake with exposure can be impossible to recover.

Cheers,
Bernard
Not trying to turn this into a "film vs digital", but:
If a given imaging technology can produce discernible details from a large window of dynamic range (lets say 14 stops), but has to store it within a format that has limited SNR (lets say 100:1, 8 bits or whatever), there are limits to what you can recover (apply a new non-linear transform) before noise will be apparent.

I think this applies to film as well as JPEG files.

If some camera did in-camera processing of raw files, that would be similar to what film-cameras does to the film (or how the film inherently works). So lets say that controlled by camera parameters such as ISO, a spatial lowpass filter (or median, bilateral, whatever) was used for the dark range of the pixels, smoothing out noise and making (hopefully) real detail more apparent against the noise, although smeared. Would that be a higher DR camera? Higher DR as measured by DXO, higher DR as visually inspected by its users?

-k
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 02, 2010, 07:06:46 am
Google chrome reports it as 0KB when I download it.

-h

I believe it's now fixed. Must have been caused by a quantum fluctuation.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 02, 2010, 09:45:31 am
Of course, those who are skeptical might well wonder if the first stop was an equal ETTR for both cameras. Perhaps the D7000 received an effectively greater exposure than the 50D, which might partly explain the 2-stop difference in DR.

To allay any such concerns that critical readers may have, I show here the ACR window for each RAW file at the maximum exposure of 4 seconds, showing the results of the auto feature which applies a -0.8 EC adjustment to the 50D file and a -0.7 EC adjustment to the D7000 file.

The target was printed on Epson Enhanced Matte, and the RGB values of the white border of the paper, at approx. the same position in each image, are shown to the left of the histograms.

I think we can reasonably state that the 50D does not have an exposure disadvantage.

The 13th stop for the D7000 is 1/1,000th of a sec. The 11th stop for the 50D is 1/250th.
Title: Re: Nikon D7000 Dynamic Range
Post by: bjanes on December 02, 2010, 11:34:28 am
If some camera did in-camera processing of raw files, that would be similar to what film-cameras does to the film (or how the film inherently works). So lets say that controlled by camera parameters such as ISO, a spatial lowpass filter (or median, bilateral, whatever) was used for the dark range of the pixels, smoothing out noise and making (hopefully) real detail more apparent against the noise, although smeared. Would that be a higher DR camera? Higher DR as measured by DXO, higher DR as visually inspected by its users?

One way to check for filtering of the raw data is to perform a Fourier analysis as Guillermo Liujk (http://www.luminous-landscape.com/forum/index.php?topic=49200.0;topicseen) did in an analysis for the Pentax camera that uses the same Sony sensor as does the Nikon D7000. He found no evidence of any filtration.

Regards,

Billo
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 03, 2010, 06:11:43 pm
Not trying to turn this into a "film vs digital", but:
If a given imaging technology can produce discernible details from a large window of dynamic range (lets say 14 stops), but has to store it within a format that has limited SNR (lets say 100:1, 8 bits or whatever), there are limits to what you can recover (apply a new non-linear transform) before noise will be apparent.

I think this applies to film as well as JPEG files.

If some camera did in-camera processing of raw files, that would be similar to what film-cameras does to the film (or how the film inherently works). So lets say that controlled by camera parameters such as ISO, a spatial lowpass filter (or median, bilateral, whatever) was used for the dark range of the pixels, smoothing out noise and making (hopefully) real detail more apparent against the noise, although smeared. Would that be a higher DR camera? Higher DR as measured by DXO, higher DR as visually inspected by its users?

-k

As far as I understand, the limits to the DR that can be recorded on a linear device such as a digital camera's sensor, are governed by factors such as the level of noise in the camera, including shot noise within the detection system as well as shot noise inherent in the received signal, the size of the pixels (full-well capacity), and the number of 'bits' in the camera's internal computer processor such as its analog-to-digital converter and other amplifiers.

I believe the 14-bit system now used in current DSLRs is theoretically capable of recording 2 stops more DR in the shadows than the older 12-bit systems, provided camera noise levels are sufficiently low.

Having recorded that wide dynamic range (say 14 stops), whether using a digital camera or some special high-DR film, the latent image in the RAW file, or on the exposed film, has to be developed before the image can be seen.

Those who are familiar with wet-darkroom practices would choose their developer carefully, in accordance with film type, in order to extract maximum detail from the shadows. When making a print from the developed film, they would also choose the paper-type carefully if they wanted to bring out detail in the shadows. For example, a high contrast paper would tend to clip the shadows to black and reduce the apparent DR. A low contrast paper would be preferred, plus the application of some degree of dodging and burning during the exposure of the photographic paper under the enlarger.

The RAW file from a digital camera is analagous to an exposed, but undeveloped, piece of film. Like the exposed film it has to be 'developed' before the image can be seen, but developed in the digital domain, in Lightroom or ACR etc.

In order to 'see' any detail or information in the shadows, the shadows need to be lifted. The dark areas need to be lightened and sometimes the light areas need to be darkened. Tone curves need to be applied.

Once the image has been processed in such a manner so that the image on monitor closely simulates what the eye saw at the time the shot was taken, I don't see any problem in converting the 16 bit file to 8 bits and compressing to jpeg. Any loss in quality will be marginal, provided the best quality of compression is used. The higher bit levels are useful for processing purposes, but 8 bits per color is considered sufficient for viewing purposes.

However, in the above description, I have assumed that the goal is to make an accurate representation of what the eye saw when the shot was taken. This is not always the goal of photography. One can attempt to be creative and try to improve upon reality.

Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 05, 2010, 12:28:12 am
Okay! What about the 9th stop in the DR range? 9 stops of DR was considered a useful range for color negative film. It gave a reasonable leeway for overexposure.

Even BJL would surely not turn up his nose at detail in the 9th stop. Is such detail usable on a modern 35mm cropped-format DSLR?

Well, on the D7000 is certainly appears to be. But I'm not sure about the Canon 50D.  (The 60D would have very marginally better DR, tonal range & color sensitivity than the 50D at base ISO, but not above base ISO.)

These files are crops of the centre of Jonathan Wienke's DR Test Target. Their purpose is to show the 'real' value of an extended dynamic range. Forget noise! That's just one parameter. Can you see the detail despite the noise?  That's the true test.

I'm showing here  a centre crop of the test target, but the LL site is telling me that the file is too big, although it is definitely under 4MB after de-compression, so I'll show you the D7000 crop in this thread, and the 50D crop in the next thread.

These 9th stops are at an exposure of 1/60th sec, as opposed to the full ETTR exposure of 4 seconds, of the same target under the same lighting conditions.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 05, 2010, 12:33:04 am
This the Canon 50D centre crop of the same target at the same exposure. Here's crossing my fingers that the noise will not be too great for the system to handle  ;D .
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 05, 2010, 12:44:56 am
Weird! The colors in the D50 crop seem much more muted than they do on my monitor prior to download. Ill try a reduced size comparison of the two together.

That's closer. What's going on? Some more quantum fluctuations perhaps.

I should mention that no noise reduction or sharpening has been applied to these images. They've been converted in ACR 6.3 beta using EC, brightness and contrast level, to equalize the appearance of the images as closely as possible.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 05, 2010, 01:38:04 am
Have failed to download the 50D crop after several attempts. I get an error message which suggests that my download speed might be too slow. I'm on ADSL2.
Title: Re: Nikon D7000 Dynamic Range
Post by: hjulenissen on December 06, 2010, 04:29:50 am
Ray:
We fully agree that the specs needed for capture are different from those needed for presentation. When "developing" the captured data into a human-observable image, all kinds of non-linear/linear transforms can be carried out to make the end-result more visually similar to the original scene, or just to make it subjectively pleasing.

My point was that it may (and I am just speculating here) make more sense to talk about DR and SNR at different input levels in one go. Having 20 stops of sensor DR may not help that much if most of that range is very low SNR? Having 14 stops of discernible information (film) may not make that much sense if the non-linear process needed to even out the inherent non-linearity makes it noisy to look at.

So what I was hoping for was to overlaid curves, with input level on the x-axis, and output level and noise level plottet. The "window" between those two should define the signal-dependent DR at a range of input levels, right?

I am struggling with shot-noise being signal dependent, and not additive. Perhaps my post is just jibberish.

-h
Title: Re: Nikon D7000 Dynamic Range
Post by: JR on December 06, 2010, 12:23:04 pm
Hi, Ray! I like your D7000 Dynamic Range post.  :) I share your conclusions and wish Canon will come up with better DR sensors. Especially the shadow DR should be improved. Highlights are good I think. With HTP on you get about 4.5 stops of DR in the highlights which is as good as it gets.

It seems like many do not care about DR and some even think you are crazy when you empathize this. I don´t. I have invested time and money in my Canon gear and know how to get the best out of it but I still think they need to work on their sensors. I don´t know if they have "fallen behind" or if they just don´t put any effort in to improving DR? I believe it is a marketing issue. They have been focused on video for a long time now. The average mass consumer don´t care about better shadow DR. They care about video and features. Canon give them what they want. I think that is the main reason Canon is lagging behind with respect to DR in the shadows. Whether Canon think they need to improve DR or not I don´t know but my guess would be that they don´t care about it at the moment. Only if they see a huge demand for better DR they will do something about it, thus I doubt we will see 14 stops of DR in any Canon camera for at least 2-3 years if at all. It is only a guess of course but it is based upon what we have seen from Canon the past 5-6 years.

I have tried Nikon and there is no doubt that they have better shadow DR. I can easily lift the shadows in post and do not have to worry about banding or posterization. And I am not taking about extreme editing. Only moderate editing. The D7000 is doing exceptionally well in this regard. It deserves a gold medal  :)

I am not going to trade in my Canon gear. It is too expensive to change brand and I am not sure if it is worth it. Not at the moment.
Title: Re: Nikon D7000 Dynamic Range
Post by: PierreVandevenne on December 06, 2010, 08:01:53 pm
It seems like many do not care about DR and some even think you are crazy when you empathize this. I don´t. I have invested time and money in my Canon gear and know how to get the best out of it but I still think they need to work on their sensors.
I am not going to trade in my Canon gear. It is too expensive to change brand and I am not sure if it is worth it. Not at the moment.

It really seems Sony sensors have the edge at this point. That's an undeniable fact. Reading their technical litterature, what they do at the individual pixel is quite amazing. I was particularly impressed by their A/D converter (fig 3 in this page http://www.sony.net/SonyInfo/technology/technology/theme/cmos_02.html). Just as Nikon was way behind Canon before they started using Sony sensors, Canon is definitely behind Sony and Pentax now (note: I am mostly a Canon owner myself). I am sure Canon would like to catch up, no so sure they can match Sony on sensors though. The K5 images are _really_ impressive imho.

But as you point out, focusing on other features is probably a good strategy as well: I've heard that a computer manufacturer has been quite successful in that respect, despite significantly underperforming others in terms of processing power ;-)
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 06, 2010, 10:48:17 pm
Hi, Ray! I like your D7000 Dynamic Range post.  :) I share your conclusions and wish Canon will come up with better DR sensors. Especially the shadow DR should be improved. Highlights are good I think. With HTP on you get about 4.5 stops of DR in the highlights which is as good as it gets.

Hi JR! Thanks! I'm glad at least someone appreciates all the hard work I'm doing.  :D

Extending DR means lowering noise and improving detail in the shadows. Noise is never a problem in the highlights, although shot noise can sometimes be a problem in the mid-tones.

Quote
With HTP on you get about 4.5 stops of DR in the highlights which is as good as it gets.


You probably know already that HTP surreptitiously drops the ISO setting down a stop, so with HTP activated, you are effectively underexposing your image in relation to your chosen ISO setting by one stop. The consequences are more noise in the shadows. Of course, it's usually preferrable have a bit of additional noise in the shadows than blow the highlights, which is why some folks find HTP useful. I personally prefer to auto-bracket exposure.

The D7000 would have no need for HTP when shooting RAW. Whatever ISO you're at, if you are at all worried about losing highlight detail, just drop down to base ISO. I imagine, if one is at ISO 6400 shooting a night scene with artificial light, then dropping down to ISO 100 would probably allow one see the shape, hue and color of the semi-molten filament through the transparent glass of a clear tungsten light bulb. But I haven't tried that yet.  ;D

Quote
I have tried Nikon and there is no doubt that they have better shadow DR. I can easily lift the shadows in post and do not have to worry about banding or posterization. And I am not taking about extreme editing. Only moderate editing. The D7000 is doing exceptionally well in this regard. It deserves a gold medal

I am not going to trade in my Canon gear. It is too expensive to change brand and I am not sure if it is worth it. Not at the moment.

I agree, it's probematical carrying two systems. However, I haven't made a complete switch from Canon to Nikon because I can't find an improvement on the Canon 100-400 IS zoom. The Nikkor 80-400 VR will no doubt be staunchly defended by Nikon fanboys, but from reports that I've come across, the Canon has better performance at 400mm.

Lens quality is important to me, within reason. It has to be balanced with flexibility of use, and weight and cost considerations. The Canon 100-400 has that balance right, but I wish Canon would produce an upgrade with a razor sharp performance at F5.6, at 400mm.

I take most of my photos when travelling. If I were to set off tomorrow for Nepal, I'd be carrying 3 cameras instead of the usual 2, but still 3 lenses. I'd be carrying the Nikon D700 & D7000, the Canon 50D, the Nikkor 14-24/2.8, the Nikkor 24-120/F4 and the Canon 100-400. The total weight would be slightly greater, not just because of the additional camera, the 50D, which is about an extra 800gms, but also the additional 0.5Kg of the D700 with 14-24/2.8 lens, which replaces my 5D with Sigma 15-30. Total additional weight would be of the order of 1.3Kg.

Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 06, 2010, 10:56:45 pm
Ray:
We fully agree that the specs needed for capture are different from those needed for presentation. When "developing" the captured data into a human-observable image, all kinds of non-linear/linear transforms can be carried out to make the end-result more visually similar to the original scene, or just to make it subjectively pleasing. Having 20 stops of sensor DR may not help that much if most of that range is very low SNR? Having 14 stops of discernible information (film) may not make that much sense if the non-linear process needed to even out the inherent non-linearity makes it noisy to look at.
 

As far as I understand, it's those lower stops in the DR range that are the problem regarding noise obscuring detail. In reality, one does not expect to see full detail in a shadow, but one does expect to see some detail if detail is present. One doesn't expect, when viewing a real-world scene, to suddenly see an area of total blackness in a shadow, whether such a shadow is in the corner of one's living room or at the foot of a waterfall in the rain forest, unless of course the corner is in an area, for example, which has been painted in matte black and therefore should be black.

One certainly doesn't expect to see speckled color and streaks of banding when viewing the shadows in a real-world scene with one's naked eyes.


Quote
So what I was hoping for was to overlaid curves, with input level on the x-axis, and output level and noise level plottet. The "window" between those two should define the signal-dependent DR at a range of input levels, right?

There are plenty of graphs at DXOMark and explanations of noise characteristics. It's a fairly safe bet that the lowest 2 or 3 stops at the extreme end of the DR range of any camera that DXOMark have tested, have very limited use in normal photography. Too noisy by far.

However, signal-to-noise in the shadows improves more dramatically with increases in exposure, than it does in the midtones. A doubling of exposure will increase the SNR in the shadows by about 6dB, but the same increase of exposure will increase SNR in the midtones by only 3dB.

When you underexpose your shot, ie, fail to get an ETTR, it's the shadows that suffer the most.
Title: Re: Nikon D7000 Dynamic Range
Post by: JR on December 07, 2010, 05:19:15 am
Ray, just a comment on HTP as it concerns DR :)

I am familiar with HTP. I know a lot of people don´t like the feature, they say they get to much noise in the shadows. I don´t agree with that. I like to push all my equipment to their limits, and my personal findings are completely in line with the findings of Bob Atkins.

I find that HTP gives m a little more than one stop of DR in the highlights with no extra noise in the shadows. When I say no extra noise I am looking at it from a practical point of view. I know it can be measured. I know I can see it if I enlarge the image 400% and study the shadows closely but I can´t see it in an A3+ print. I have tried and it is not possible. From a practical point of view it is a non issue for me. I therefore leave HTP on all the time. It gives med extra highlight detail at no cost.

Here´s an image from Bob´s site. As you can see you have to push pretty hard and look pretty hard to see the extra shadow noise produced by HTP. It is as Bob said, "there is an increase in the shadow noise if you look closely enough."

(http://)
Credit to Bob Atkins: http://www.bobatkins.com/photography/digital/canon_eos_40D_review_6.html#highlight2

I therefore think HTP is a "nice" feature that gives you that little extra DR in the highlights. Not by much, I know, but you take what you get from Canon  :)    I know I can "push and pull" in several ways to extend the DR of the camera, but HTP saves me time in post. I also think some people who complain about the usefulness of HTP are more busy looking at scientific measurements than actual use.

Despite my "praises" of Canon´s HTP they still have to much shadow noise. Just to be clear on that. :)   I think it is good that Nikon, Pentax and Sony ( particularly Nikon ) are coming up with these great sensors and are putting pressure on Canon.
Title: Re: Nikon D7000 Dynamic Range
Post by: JR on December 07, 2010, 05:51:15 am
http://www.sony.net/SonyInfo/technology/technology/theme/cmos_02.html)
The K5 images are _really_ impressive imho.

Thank you for the link. I agree. Sony has been in business for decades and when they now have entered the DSLR market the increased competition will benefit us all. As for the Pentax K5 it seems it is very close or identical to the D7000. I don´t have the camera so I can only speculate. I have however downloaded a bunch of raw files just to have a look at them and the only thing I am not so sure about is the apparent softness. The D7000 appears a little sharper than the K5. I have no idea why. Could be a stronger AA filter or deliberately under-sharpening. Whatever it is both cameras have excellent shadow detail. That´s what I would like to see in my Canon camera  :)
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 07, 2010, 06:48:01 am
Ray, just a comment on HTP as it concerns DR :)

I am familiar with HTP. I know a lot of people don´t like the feature, they say they get to much noise in the shadows. I don´t agree with that. I like to push all my equipment to their limits, and my personal findings are completely in line with the findings of Bob Atkins.

I find that HTP gives m a little more than one stop of DR in the highlights with no extra noise in the shadows. When I say no extra noise I am looking at it from a practical point of view. I know it can be measured. I know I can see it if I enlarge the image 400% and study the shadows closely but I can´t see it in an A3+ print. I have tried and it is not possible. From a practical point of view it is a non issue for me. I therefore leave HTP on all the time. It gives med extra highlight detail at no cost.

Here´s an image from Bob´s site. As you can see you have to push pretty hard and look pretty hard to see the extra shadow noise produced by HTP. It is as Bob said, "there is an increase in the shadow noise if you look closely enough."


JR,
That is interesting, isn't it! I would have thought that the noise in the shadows would have been greater than that, with HTP on.

I have a lot of respect for Bob Atkins. He seems to know his stuff. If he'd had more time, or the inclination, I'm sure he would not only have compared images at ISO 200 with HTP on, and off, but also compared the same exposure at ISO 100 to see how the shadows compared with the shot at ISO 200 with HTP on.  

He might also have tried comparisons at higher ISOs with HTP on, and off, to see if the difference in shadow noise was similarly negligible.

Out of curiosity, I checked the measurement data from DXO for the Canon 40D, which featured in Bob Atkins HTP test.

Surprise! Surprise! All is now clear. The reason why Bob couldn't detect any significant increase in shadow noise with HTP on, at ISO 200, is because in this model of camera, the 40D, the SNR curves for ISO 100 and ISO 200 merge into one, in the shadows.

Have a look at the attached image of the full SNR information for the 40D at various ISOs, from the DXOMark website. You should notice that the SNR curves for ISO 100 and ISO 200 merge at a point about 2/3rds of the way towards the x-axis.

However, this is not the case at any ISO above 200. If you were to compare shadow noise at ISO 3200, with HTP on, and off, I predict you would observe a substantial increase in shadow noise in the image with HTP on. At ISO 400, there would be a less substantial increase in shadow noise, with HTP on, but still noticeable.

By the way, this is yet another example of how accurate DXO tests really are.
Title: Re: Nikon D7000 Dynamic Range
Post by: telyt on December 07, 2010, 10:55:42 am
I have a lot of respect for Bob Atkins. He seems to know his stuff.

He lost any shred of respect I had for him when he "graded" a camera he has never used, and defended his "grade" of it in the face of contrary evidence from people who had used the camera.
Title: Re: Nikon D7000 Dynamic Range
Post by: Dennis Carbo on December 07, 2010, 01:15:58 pm
He lost any shred of respect I had for him when he "graded" a camera he has never used, and defended his "grade" it in the face of contrary evidence from people who had used the camera.

Exactly How I feel about all the people that speak in absolutes about specs and charts, this system vs. that system etc.  without ever actually putting their hands on that system. Its like expressing your opinion about a restaurant you never ate at !
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 07, 2010, 06:07:01 pm
Exactly How I feel about all the people that speak in absolutes about specs and charts, this system vs. that system etc.  without ever actually putting their hands on that system. Its like expressing your opinion about a restaurant you never ate at !


But in this example, Bob did put his hands on the camera, the 40D, and his results in respect of increased shadow noise with HTP on, were in fact very accurate at ISO 200 (according to the DXO graphs). What Bob should have done was extend his testing to higher ISOs, and then he would have seen the anomaly that shadow noise is the same in the 40D at ISO 100 and 200 only, irrespective of HTP considerations.

It almost seems as though Canon have deliberately designed the 40D this way in order to give the impression that HTP has no downside, knowing that most shots by most peopleare taken at either ISO 100 or 200.
Title: Re: Nikon D7000 Dynamic Range
Post by: hjulenissen on December 08, 2010, 05:00:27 am
It almost seems as though Canon have deliberately designed the 40D this way in order to give the impression that HTP has no downside, knowing that most shots by most peopleare taken at either ISO 100 or 200.
Do you mean that they willingly limited the performance of ISO100 so as to hide the drawbacks of a mode that few (?) people use. I find that hard to belive. Is there no physical mechanism that explains the anomaly of iso100/200 at low input levels?

-h
Title: Re: Nikon D7000 Dynamic Range
Post by: ejmartin on December 08, 2010, 08:03:02 am
Do you mean that they willingly limited the performance of ISO100 so as to hide the drawbacks of a mode that few (?) people use. I find that hard to believe. Is there no physical mechanism that explains the anomaly of iso100/200 at low input levels?

-h

Yes there is.  Canon cameras have a read noise profile (the noise the camera adds when reading the sensor) that looks like this as a function of ISO (this for my 1D3):

(http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/1D3_noisesq_vs_iso-elec.png)

Since ISO 2oo (ie ISO 200 w/HTP) internally in the camera uses the amplification of ISO 100, the noise relative to signal is approximately double what one would get by using straight ISO 200.  Read noise is most noticeable in shadows (low signal/noise) so that is where the difference will show most noticeably.  By the time one gets to ISO 1600, there is essentially no difference between that and ISO 16oo (using internally the amplification of ISO 800, the difference is very slight).

Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 08, 2010, 10:38:47 am

Since ISO 2oo (ie ISO 200 w/HTP) internally in the camera uses the amplification of ISO 100, the noise relative to signal is approximately double what one would get by using straight ISO 200.  Read noise is most noticeable in shadows (low signal/noise) so that is where the difference will show most noticeably.  By the time one gets to ISO 1600, there is essentially no difference between that and ISO 16oo (using internally the amplification of ISO 800, the difference is very slight).

Emil,
There's something odd going on here. The DXO Full SNR graphs for each ISO show that the 40D at ISO 100 has no better SNR than at ISO 200, in the shadows.

I interpret that as meaning that a given exposure at ISO 200 with HTP activated, will produce the same results as at ISO 100, where HTP is not an option, using the same exposure.

The principle has been with Canon cameras, that it's always better to fully expose at a higher ISO than use the same exposure to underexpose at a lower ISO, regarding shadow noise.

This doesn't appear to be the case with the 40D at ISO 200.

If one examines the DXO full graphs for SNR at each ISO, one sees that the earliest Canon APS-C camera that DXOMark have tested, the 6mp 10D, has a clear distinction in SNR between ISO 100 & 200, in the shadows.

The 20D has a much less significant distinction, the 30D even less, and the 40D none at all, except very close to the camera's noise floor where there's a slight blip in favour of ISO 100.
I'm speculating that this situation has arisen due to increased pixel count and smaller pixels.

The 50D seems to reflect the reality of this situation by making ISO 100 and ISO 200 the same sensitivity. I didn't realise this until I checked the DXO test results.

Here are the DXO graphs for the 40D and 50D. Could you explain what's going on here, please.  :)

Title: Re: Nikon D7000 Dynamic Range
Post by: bjanes on December 08, 2010, 02:37:56 pm
Emil,
There's something odd going on here. The DXO Full SNR graphs for each ISO show that the 40D at ISO 100 has no better SNR than at ISO 200, in the shadows.

Here are the DXO graphs for the 40D and 50D. Could you explain what's going on here, please.  :)

While waiting for Emil's reply, I will add this observation which may be pertinent. Looking at the ISO plots for the 40D and 50D, I see that the ISO of the 50D, as measured by DXO, is the same for ISO 200 and ISO 100, which leads me to believe that the real base ISO of the 50D is 200 and that the ISO of 100 is merely overexposure. This is what I have observed for my Nikon D3, where the results ab the base ISO of 200 are exactly the same as for the LoISO setting of 100.

For the 40D, the real base ISO appears to be close to a nominal value of 100 (the measured ISO is actually 87 and the other measured ISOs are also proportionally smaller than the nominal values). What a wealth if information in the DXO database!

Regards,

Bill

Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 08, 2010, 09:40:11 pm
While waiting for Emil's reply, I will add this observation which may be pertinent. Looking at the ISO plots for the 40D and 50D, I see that the ISO of the 50D, as measured by DXO, is the same for ISO 200 and ISO 100, which leads me to believe that the real base ISO of the 50D is 200 and that the ISO of 100 is merely overexposure. This is what I have observed for my Nikon D3, where the results ab the base ISO of 200 are exactly the same as for the LoISO setting of 100.

For the 40D, the real base ISO appears to be close to a nominal value of 100 (the measured ISO is actually 87 and the other measured ISOs are also proportionally smaller than the nominal values). What a wealth if information in the DXO database!

Bill, I should thank you for bringing to my attention that secod tier of headings which is not available in the 'Compare Sensor' mode which I've always previously referred to.

I've taken several thousand shots with my 50D; most of them on a recent trip to Europe and Russia, and I'm embarrassed to admit I had no idea that ISO 100 on this camera has identical performance to ISO 200, regarding highlight detail and shadow detail, at appropriately different exposures.

In other words, 1/50th at ISO 100 produces the same result as 1/100th at ISO 200; identical for all practical purposes.

The reason why DXO do not show an SNR curve for the 50D at ISO 100 is because it would be impossible to see it. It would lie exactly underneath the SNR curve for ISO 200.

I've just stepped outside onto the verandah to take a few bracketed shots of the cloudy sky, at ISO 100 & 200. An ETTR exposure at 1/640th and ISO 200 produces the same result as 1/320th at ISO 100. The same degree of negative EC in ACR is required in each case. The same amount of detail is visible in the clouds. The histogram of each shot is approximately the same, indicating both exposures are a full ETTR.

I then stepped back into the house and took some severely underexposed shots of Jonathan's DR Test Target, at ISO 100 and 200, expecting the ISO 100 shot at 1/50th might display noticeably less noise than the ISO 200 shot at 1/100th.

Nope! The images are indistinguishable. They are identical for all practical purposes.

Well I never!  ;D  It's seems that this camera has two base ISOs.  ;D
Title: Re: Nikon D7000 Dynamic Range
Post by: JR on December 09, 2010, 04:57:23 am
That´s right, the 50D seems to have two "base" iso´s. Good to know if you are an iso 100 photographer but need the speed of iso 200  :)

If you look closely at the SNR number provided by Dxomark you will see that even if the max SNR between selected cameras does not differ that much the SNR in the deep shadows does. Below are screen shots of a few models, looking at the SNR in the deep shadows, just above 1% gray. I think 1% gray qualifies as "deep" shadows.  :)

The 60D has marginally improved in the shadows.

The measured points are not exactly the same but they are close enough.

Below is max SNR for the same cameras. Note the difference between the 50D and the D700/K5.

50D -          SNR:    40,5dB
5D Mark II - SNR:    43,1dB
D700 -        SNR:    44,8dB
D7000 -      SNR:    44,3dB
K5 -           SNR:    44,7dB
60D -         SNR: 41,1dB
Title: Re: Nikon D7000 Dynamic Range
Post by: JR on December 09, 2010, 05:00:48 am
D700 and 60D SNR @ 1% gray
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 09, 2010, 10:45:45 am
That´s right, the 50D seems to have two "base" iso´s. Good to know if you are an iso 100 photographer but need the speed of iso 200  :)

It's good to know whatever type of photographer you are. The only reason I can think of why anyone would want to use ISO 100 on the 50D is if they wanted to deliberately create a blur for a particular effect, such as depiction or emphasis of movement. A shutter speed which is unnecessarily fast is generally preferrable to one which is too slow.

Quote
If you look closely at the SNR number provided by Dxomark you will see that even if the max SNR between selected cameras does not differ that much the SNR in the deep shadows does. Below are screen shots of a few models, looking at the SNR in the deep shadows, just above 1% gray. I think 1% gray qualifies as "deep" shadows.


No. This is a logarithmic scale. The deep shadows would be around 0.1% and below. Don't ask me to explain. I'm not a mathematician. However, DXOMark state specifically that a change of one stop (or 1 EV) of exposure results in a change of about 3dB in SNR in the midtones, but a change of about 6dB in the shadows.

Title: 1% gray is 4-stops below normal midtones, in the deep shadows
Post by: BJL on December 09, 2010, 11:20:01 am
With a typical mid-tone placement, traditionally 18% gray (18% reflectance), in practice often a bit lower, like 13%, the 1% gray level is about four stops below the midtones. To be pedantic, it is 4 stops below 16% gray.

That level of "fours stops below midtones" is what is the zone system describes as providing only vague textural information, not real subject detail, which typically ends 3 stops below mid-tones. To give you an idea of how dark 1% gray looks, it is below the reflectance of the purest black of most or all photographic printing papers. Also, four stops below mid-tones is the level at which the ISO definition of film speed requires signal to be just barely above the "noise level" of "film-base plus fog", so more or less the floor for useful "signal" with film used at its rated ISO speed.

So yes, I would say that 1% gray is deep shadow.


P. S. Here is some information on the related topic of albedo, the percentage reflectance of sunlight, which seems a natural measure for daylight photography
http://en.wikipedia.org/wiki/Albedo
One highlight:
"Albedos of typical materials in visible light range from up to 0.9 for fresh snow, to about 0.04 for charcoal, one of the darkest substances."
So 1% gray is two stops blacker than charcoal, and this real-world reflectivity range from fresh snow to charcoal (critical when photographing snowmen!) is about 23:1, or 4.5 stops.
Title: Re: 1% gray is 4-stops below normal midtones, in the deep shadows
Post by: JR on December 09, 2010, 01:53:39 pm
BJL,

Thank you. Excellent explanation.

Even if we look at SNR at lets say 3-4% gray or 0.1% ( as Ray suggests ) the latest generation sensors from Sony has better SNR in the shadows compared to some Canon cameras.

-John

With a typical mid-tone placement, traditionally 18% gray (18% reflectance), in practice often a bit lower, like 13%, the 1% gray level is about four stops below the midtones. To be pedantic, it is 4 stops below 16% gray.

That level of "fours stops below midtones" is what is the zone system describes as providing only vague textural information, not real subject detail, which typically ends 3 stops below mid-tones. To give you an idea of how dark 1% gray looks, it is below the reflectance of the purest black of most or all photographic printing papers. Also, four stops below mid-tones is the level at which the ISO definition of film speed requires signal to be just barely above the "noise level" of "film-base plus fog", so more or less the floor for useful "signal" with film used at its rated ISO speed.

So yes, I would say that 1% gray is deep shadow.


P. S. Here is some information on the related topic of albedo, the percentage reflectance of sunlight, which seems a natural measure for daylight photography
http://en.wikipedia.org/wiki/Albedo
One highlight:
"Albedos of typical materials in visible light range from up to 0.9 for fresh snow, to about 0.04 for charcoal, one of the darkest substances."
So 1% gray is two stops blacker than charcoal, and this real-world reflectivity range from fresh snow to charcoal (critical when photographing snowmen!) is about 23:1, or 4.5 stops.
Title: Re: Nikon D7000 Dynamic Range
Post by: ejmartin on December 09, 2010, 05:22:26 pm
Emil,
There's something odd going on here.

[snip]

Here are the DXO graphs for the 40D and 50D. Could you explain what's going on here, please.  :)

Low ISO read noise drops by nearly a factor of two (in photon equivalents, ie electrons) between ISO 100 and 200 on most Canons, and since signal in these SNR plots is relative to clipping, in terms of absolute exposure one has half the read noise and half the signal, for about the same SNR.  When the read noise drops to being more level as a function of ISO, then the curves separate, since the read noise is the same but signal drops with ISO for a fixed percentage of clipping.  But note that even at ISO 100, there is still a SNR advantage above deep shadows since the read noise is less important and it comes down to more photons being gathered at a given percentage of clipping, when the ISO is lower.
Title: Re: 1% gray is 4-stops below normal midtones, in the deep shadows
Post by: Ray on December 09, 2010, 09:34:02 pm
With a typical mid-tone placement, traditionally 18% gray (18% reflectance), in practice often a bit lower, like 13%, the 1% gray level is about four stops below the midtones. To be pedantic, it is 4 stops below 16% gray.

That level of "fours stops below midtones" is what is the zone system describes as providing only vague textural information, not real subject detail, which typically ends 3 stops below mid-tones. To give you an idea of how dark 1% gray looks, it is below the reflectance of the purest black of most or all photographic printing papers. Also, four stops below mid-tones is the level at which the ISO definition of film speed requires signal to be just barely above the "noise level" of "film-base plus fog", so more or less the floor for useful "signal" with film used at its rated ISO speed.

So yes, I would say that 1% gray is deep shadow.


P. S. Here is some information on the related topic of albedo, the percentage reflectance of sunlight, which seems a natural measure for daylight photography
http://en.wikipedia.org/wiki/Albedo
One highlight:
"Albedos of typical materials in visible light range from up to 0.9 for fresh snow, to about 0.04 for charcoal, one of the darkest substances."
So 1% gray is two stops blacker than charcoal, and this real-world reflectivity range from fresh snow to charcoal (critical when photographing snowmen!) is about 23:1, or 4.5 stops.

BJL,
What an excellent justification for not needing a better camera than a Point & Shoot, as regards SNR and dynamic range.
However, some of us, notwithstanding the reflectivity of charcoal, wish for lower noise and better detail in the shadows than a P&S or even an Olympus 4/3rds can provide.  Some of us even feel the need to merge different exposures to HDR in order to get a better SNR in the shadows.

Comparing the SNR on the log scale at 1% input for various cameras at base ISO, I find that the Canon G12 manages an SNR of about 19 dB, The Olypus E-620 only 18dB, the Canon 50D 21dB, the Canon 60D 22dB and the D7000 26dB.

We can argue all day about subjective impressions of what may be considered a moderately deep shadow, a deep shadow or a very deep shadow, but a degree of shadow in which a P&S has slightly lower noise than the Olympus E-620 does not seem particularly deep to me.

What you've written above also appears to be at variance with DXOMark's own explanations of the meaning of their results.

I invite you to look at the following extract from their 'insights'  articles at
http://www.dxomark.com/index.php/en/Our-publications/DxOMark-Insights/Noise-characterization/Summary

Quote
As a consequence, the SNR also has three regimes:

Shadows:  the SNR increases 6dB for every EV and loses 6dB for each doubling of the ISO setting.

Midtones:  the SNR increases 3dB for every EV and decreases by 3dB for each doubling of the ISO setting.

Highlights:  the SNR is constant and does not depend on the ISO.

Now it so happens the SNR graphs for the D7000 lend themselves admirably to demonstrate these DXO statements, because, as you know, the D7000 can be used for all purposes at base ISO. The loss in SNR due to doubling ISO is the same as reducing exposure by one stop at base ISO

In light of the above, we can make some reasonable deductions as to what point along the x-axis of the DXO graphs the midtones and the shadows lie.

If we examine the graph for SNR at 18% grey, for the D7000, we find that there is indeed a loss of approximately 3dB for each doubling of the ISO setting.

If we search for the point along the x-axis on the Full SNR graph where a doubling of ISO produces a fall of approximately 3dB in SNR, ie. the point where 18% grey would lie, we find it's about midway between 100% and 10% on the x-axis. That point represents the midtones, approximately the tonal range of skin tones in a portrait.

If we examine the fall in SNR with each doubling of ISO at the 1% point on the x-axis, which you describe as the deep shadows, we see that between ISO 100 and ISO 6400, the SNR has fallen from 26dB to 4dB with a total change of 6 EV in exposure.

22/6=3.7dB. I hardly think this constitutes the deep shadows, an increased drop in SNR of just 0.7dB compared to the rate of fall in the midtones of 3dB.

If we examine the fall in SNR at the 0.1% point on the x-axis, which I would describe as the point where the deep shadows begin, we find there's a fall of approximately 14dB between ISO 100 and ISO 800, or 4.7dB with each doubling of ISO setting, which is still short of the 6dB mentioned by DXO.

The graphs below show the Full SNR details for the D7000, and specifically the SNR at 18% grey.

Draw your own conclusions, but I know what my eyes tell me and I've taken the trouble to shoot tests with the D7000 to demonstrate the improvement in SNR in the shadows, and the consequent imrovement in visible detail compared with other cameras in identical circumstances.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 09, 2010, 10:16:10 pm
Low ISO read noise drops by nearly a factor of two (in photon equivalents, ie electrons) between ISO 100 and 200 on most Canons, and since signal in these SNR plots is relative to clipping, in terms of absolute exposure one has half the read noise and half the signal, for about the same SNR.  When the read noise drops to being more level as a function of ISO, then the curves separate, since the read noise is the same but signal drops with ISO for a fixed percentage of clipping. 

Emil,
I understand that's the case with most Canons, which is why I've been using ISO 100 with the 50D as the default, base ISO. I'm now having second thoughts and think I should set the camera at ISO 200 as base.

Quote
But note that even at ISO 100, there is still a SNR advantage above deep shadows since the read noise is less important and it comes down to more photons being gathered at a given percentage of clipping, when the ISO is lower.

I understand from DXO's 'insight' articles and other explanations, that photonic shot noise is generally more of a problem in the midtones.

I've already compared images of bright clouds, and images of deep shadows, at ISO 100 & 200 with the 50D, and have failed to observe any significant difference in noise, detail or tonal range.

I haven't, however, compared portraits of lovely models with creamy smooth skin, taken at those ISOs.

Could we reasonably predict that the ISO 100 shots of such models, using the 50D, would show visibly smoother skin tones than the ISO 200 shots?
 
(Unfortunately, no such models are currently at hand for me to test this  ;D )
Title: Re: 1% gray is 4-stops below normal midtones, in the deep shadows
Post by: ErikKaffehr on December 10, 2010, 12:52:05 am
Hi,

Except that the white snowman may be in the sun, melting away, while that piece of charcoal may be in a deep shadow.

The image below illustrates real world outdoor contrast range. It was taken using a Konica Minolta 7D in 2005. The image was shot in raw and processed in Lightroom. Better processing would certainly be possible.

Best regards
Erik

With a typical mid-tone placement, traditionally 18% gray (18% reflectance), in practice often a bit lower, like 13%, the 1% gray level is about four stops below the midtones. To be pedantic, it is 4 stops below 16% gray.

That level of "fours stops below midtones" is what is the zone system describes as providing only vague textural information, not real subject detail, which typically ends 3 stops below mid-tones. To give you an idea of how dark 1% gray looks, it is below the reflectance of the purest black of most or all photographic printing papers. Also, four stops below mid-tones is the level at which the ISO definition of film speed requires signal to be just barely above the "noise level" of "film-base plus fog", so more or less the floor for useful "signal" with film used at its rated ISO speed.

So yes, I would say that 1% gray is deep shadow.


P. S. Here is some information on the related topic of albedo, the percentage reflectance of sunlight, which seems a natural measure for daylight photography
http://en.wikipedia.org/wiki/Albedo
One highlight:
"Albedos of typical materials in visible light range from up to 0.9 for fresh snow, to about 0.04 for charcoal, one of the darkest substances."
So 1% gray is two stops blacker than charcoal, and this real-world reflectivity range from fresh snow to charcoal (critical when photographing snowmen!) is about 23:1, or 4.5 stops.
Title: Re: 1% gray is 4-stops below normal midtones, in the deep shadows
Post by: JR on December 10, 2010, 06:42:03 am

Where is this, Erik? Var är detta?


The image below illustrates real world outdoor contrast range. It was taken using a Konica Minolta 7D in 2005.

Best regards
Erik

Title: Re: 1% gray is 4-stops below normal midtones, in the deep shadows
Post by: JR on December 10, 2010, 06:47:04 am

Thank you for that link. I have read some of their "insight" articles but have not seen that one. Will read it through.

- John


I invite you to look at the following extract from their 'insights'  articles at
http://www.dxomark.com/index.php/en/Our-publications/DxOMark-Insights/Noise-characterization/Summary

Title: Re: 1% gray is 4-stops below normal midtones, in the deep shadows
Post by: ErikKaffehr on December 10, 2010, 11:10:57 am
Hi,

Det är i Österrike nära Dachstein tror jag.

Hälsningar
Erik


http://www.silberkar.com/

Where is this, Erik? Var är detta?

Title: my comment was on what 1% diffuse reflectance looks like
Post by: BJL on December 10, 2010, 01:48:13 pm
BJL,
What an excellent justification for not needing a better camera than a Point & Shoot, as regards SNR and dynamic range.
However, some of us, notwithstanding the reflectivity of charcoal, wish for lower noise and better detail in the shadows than a P&S or even an Olympus 4/3rds can provide.
And once again, your respond to my factual posting not by refuting my claims but by making personal, insulting insinuations about camera choice an such that have nothing to do with what I said. I was talking about how dark something of 1% gray (1% diffuse reflectance) looks, or how one is likely to want it to look in a displayed image, nothing more. Answer: very, very dark.

I will confine my replies to calm, factual responses like Erik's.
Title: Re: Nikon D7000 Dynamic Range
Post by: BJL on December 10, 2010, 02:54:58 pm
Except that the white snowman may be in the sun, melting away, while that piece of charcoal may be in a deep shadow.
Indeed. I was addressing the issue of handling subjects of various albedos under similar levels of incident lighting when optimum low ISO speed can be used, and the basic conclusion is that the DR needs for that situation are modest. That is, the principal need for wide DR at base ISO speed is in scenes with high subject brightness range (SBR) due to wanting to place the midtones in one, relatively dimly lit, part of the scene while avoiding blown-out highlights in other far more brightly lit parts of the scene. For this what the camera needs is lots of "highlight headroom" above the light levels being received from the adequately exposed though dimly lit subject matter. Evidence from sources like DXo indicate that with the current state of the art of DSLR sensors, the way forward in handling high SBR at base ISO speed has become a matter of improving photo-electron counting headroom capacity, not further reduction of dark noise. (It is a different story with light-starved "high ISO" situations like fast action photography, where one might have to accept exposures so low that the final images have visible shot noise, and then dark noise can make a visible contribution.)
 
To rephrase my argument from earlier, to control shot noise in the dimly lit midtones, the camera needs to gather enough light from that dimly lit region, which requires detection of about 500 or more photons from the "18% gray" subject matter within that dimly lit region, and so 100 photons or more even from charcoal (4%) in that same dim light, and thus over 10e- of shot noise from anything in that dim lighting level. Thus even the darkest (meaning least reflective) parts in that dimly lit region will have shot noise that overwhelms the 2 or 3 e- of dark noise that the best current DSLR sensors reportedly have. (The only alternative is exposure levels and photo-electron counts so low that one has highly visible shot noise in the midtones, at which case there is little point worrying about visible dark noise in the charcoal.) Any part of the scene sending out less light than charcoal in the most dimly lit regions of interest can surely be rendered as black, and will be on any print once the midtones are appropriately placed.

Thus, once exposure is adequate to control shot noise in these more dimly lit parts of the scene, the remaining challenge is entirely in the realm of "highlight headroom": being able to handle the far higher photon counts coming from other, far more brightly lit parts of the scene, like sunlit clouds or snow visible through the open window of a heavily shadowed church interior, without ND filters, and with a single exposure rather than relying on HDR blending or such. The challenge going forward for photographing such scenes of unusually high subject brightness range seems to be mostly or entirely in photon counting headroom, and progress there will likely have little or nothing to do with further reduction of dark noise. Adding one stop of DR by just halving the dark noise level of the D7000's sensor to about 1e- would be useless in this situation, or any low ISO speed situation I can imagine.

By the way, I believe that the far smaller photosites of good "compact digicam" sensors have had dark noise levels of 2e- or less for some years, so their DR limitations at base ISO speed have already been dominated by the limited electron well capacity of their small photosites.
Title: Re: 1% gray is 4-stops below normal midtones, in the deep shadows
Post by: BJL on December 10, 2010, 03:06:23 pm
The image below illustrates real world outdoor contrast range. It was taken using a Konica Minolta 7D in 2005. The image was shot in raw and processed in Lightroom. Better processing would certainly be possible.

Best regards
Erik
By the way, that is a nice shot, and good handling of a situation quite typical of the ones where I most often struggle with high subject brightness range. (Aside: I prefer to use established photographic terms like SBR rather than electrical engineering terms like DR that are currently fashionable in digital photography.) And with scenes like that, getting enough light from the shaded regions to avoid noise is not my main problem, it is blowing out the sky!
Title: Re: 1% gray is 4-stops below normal midtones, in the deep shadows
Post by: JR on December 11, 2010, 08:32:08 am

Det er et fint bilde. Jeg tenkte at du kanskje hadde tatt deg en tur over grensen til Norge. Vi har jo mye fjell og daler her.


Hi,

Det är i Österrike nära Dachstein tror jag.

Hälsningar
Erik


http://www.silberkar.com/

Title: Re: 1% gray is 4-stops below normal midtones, in the deep shadows
Post by: JR on December 11, 2010, 08:38:32 am

I think we have to ask DxoMark if we want to know exactly where the deep shadows begin. It could be that you are right, that 0.1% gray is the answer. I think only Dxomark knows the answer. Another question is of course how do they define "deep shadows"?

In general 1% gray is considered very deep shadows, as BJL wrote, but I read the link you provided to their "Insight" articles and the logarithmic scale can only be interpreted by Dxomark themselves. Interesting reading.

What is clear however is that the D7000 has excellent SNR also at 0.1% gray. Actually a bit better than the D700. And that is quite an achievement.




...DXOMark's own explanations of the meaning of their results...

...the SNR also has three regimes...

Title: Re: 1% gray is 4-stops below normal midtones, in the deep shadows
Post by: ErikKaffehr on December 11, 2010, 09:22:47 am
Nej, tyvärr!

Kanske 2011 ?

MVH
Erik

Det er et fint bilde. Jeg tenkte at du kanskje hadde tatt deg en tur over grensen til Norge. Vi har jo mye fjell og daler her.


Title: Re: 1% gray is 4-stops below normal midtones, in the deep shadows
Post by: Ray on December 11, 2010, 12:05:04 pm
I think we have to ask DxoMark if we want to know exactly where the deep shadows begin. It could be that you are right, that 0.1% gray is the answer. I think only Dxomark knows the answer. Another question is of course how do they define "deep shadows"?

In general 1% gray is considered very deep shadows, as BJL wrote, but I read the link you provided to their "Insight" articles and the logarithmic scale can only be interpreted by Dxomark themselves. Interesting reading.

What is clear however is that the D7000 has excellent SNR also at 0.1% gray. Actually a bit better than the D700. And that is quite an achievement.

I don't think you don't need to ask anyone where deep shadows begin. Use your eyes. I've never found any difficulty in determining what is in shade, what's not in shade and what is in deep shade.

There seems to be confusion here between the range of input signals (from the scene being photographed) and the range of output signals as displayed on print or monitor.

A 1% grey patch is certainly a dark shade of grey and might be quite appropriate for the display of deep shadows on a print. However, in a high contrast, real-world scene where a white cloud is 100% grey, 1% on a logarithmic scale is not particularly dark.

At the 1% point on the DXO graph of the D7000, the signal has dropped only 15dB from its full-well capacity. The dynamic range of real-world scenes in sunny conditions can be as high as 100dB, even higher.

You think just 15dB down, at the 85dB point of a very bright and high-contrast scene, we're into deep shadows. Pull the other leg.  ;D

Even if we take a less extreme example, say a scene of 60dB dynamic range, do you think we're into deep shade at the 45dB point on the scale?
Title: Re: Nikon D7000 Dynamic Range
Post by: JR on December 11, 2010, 01:12:53 pm


G´Day Ray,

I think we are talking about two different things. I am talking about the D7000 sensor, Dxomark and where to place the deep shadows.  :)  Not a real world situation with a 100dB high contrast scene.

At 0.1% grey ( logarithmic scale ) the SNR is ca 16dB for the D7000. The 50D´s SNR is just above 6dB. That is very low. What do you think? Would you consider 6dB deep shadows? According to this link http://www.dxomark.com/index.php/en/Learn-more/DxOMark-database/Measurements/Noise  they say: the lowest gray luminance makes sense only if it is not drowned by noise, thus this lower boundary is defined as the gray luminance for which the SNR is larger than 1. 6dB= 1EV  We are close to hitting the floor.

Scene dependent DR and SNR is another subject and of course I agree you have to trust your eyes when defining the shadow region as every scene can be different. As long as I keep my monitor calibrated and my reading glasses clean I usually do.  :)

- John
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 11, 2010, 06:39:21 pm

G´Day Ray,

I think we are talking about two different things. I am talking about the D7000 sensor, Dxomark and where to place the deep shadows.  :)  Not a real world situation with a 100dB high contrast scene.

At 0.1% grey ( logarithmic scale ) the SNR is ca 16dB for the D7000. The 50D´s SNR is just above 6dB. That is very low. What do you think? Would you consider 6dB deep shadows? According to this link http://www.dxomark.com/index.php/en/Learn-more/DxOMark-database/Measurements/Noise  they say: the lowest gray luminance makes sense only if it is not drowned by noise, thus this lower boundary is defined as the gray luminance for which the SNR is larger than 1. 6dB= 1EV  We are close to hitting the floor.

Scene dependent DR and SNR is another subject and of course I agree you have to trust your eyes when defining the shadow region as every scene can be different. As long as I keep my monitor calibrated and my reading glasses clean I usually do.  :)

- John


John,
Current cameras are not capable of simultaneously recording meaningful detail in deep shadows and in bright highlights. It's why people use fill-flash where possible, or merge multiple exposures to HDR, or render such deep shadows black on the print.

We're both looking at the same graph, the Full SNR graph for the D7000 for example, and what I see on the x-axis is a representation of an input signal. What I see on the y-axis is the camera's response to that input signal.

At an input of 1% luminance on the log scale, the SNR of the camera has fallen by 15-18dB. At 100% luminance its DR is close to 14 EV. At an input of 1% grey its DR is still a very healthy 8 EV.

Unfortunately, those last couple of stops of DR are a bit noisy and useless, so 11 or 12 EV of DR for the D7000 would be a more reasonable estimate. At a 1% input level, the very limited D7000, which is incapable of capturing the full dynamic range of a very bright scene with deep shadows, has still got 5 or 6 stops of useable DR.

Yeah!! Yeah! Please give me a camera that still has 5 to 6 useable stops of DR when I record those deep shadows in a rainforest and the white rocks by the waterfall glistening in the sun.

Surely it's apparent from those DXO graphs, if an input signal of 1% grey really is representative of a deep shadow, then any P&S camera will suffice. As I mentioned before, even the Canon G12 has a healthy SNR of 19dB at a 1% input signal.

Perhaps part of the problem is that some of you guys who live in Northern Europe don't realise how bright the sun is in Australia. Perhaps most of your photos are taken on dull, cloudy days.  ;D

By the way, the shadows should always be placed at a point which does not result in a blow-out of the highlights, if the highlights are important. I really don't care much for landscapes with clouds that show no detail and skies that appear more cyan than blue.
Title: Re: Nikon D7000 Dynamic Range
Post by: bjanes on December 11, 2010, 08:06:53 pm
By the way, I believe that the far smaller photosites of good "compact digicam" sensors have had dark noise levels of 2e- or less for some years, so their DR limitations at base ISO speed have already been dominated by the limited electron well capacity of their small photosites.

That is true, but a read noise of 2e- with a small pixel has much more significance than a similar read noise for a large pixel when the electron count is converted to a 12 or 14 bit data number because of gain (electrons/data number). See Table 3 of Roger Clark's essay (http://www.clarkvision.com/articles//does.pixel.size.matter/#Example_Noise).

Regards,

Bill
Title: Re: Nikon D7000 Dynamic Range
Post by: JR on December 12, 2010, 07:51:31 am

...some of you guys who live in Northern Europe don't realise how bright the sun is in Australia. Perhaps most of your photos are taken on dull, cloudy days.  ;D


Sunshine? What is that?  :D

A friend of mine is an Aussie. He used to do a lot of bush-hiking when he was younger and he has told me how extremely bright it can be. And hot. Really hot. Not Europe-hot but down-under hot  :)

Dull, cloudy days are not a photographic problem in the northern hemisphere, but a long dark winter & short days with only a couple of hours of twilight is.

- John
Title: Re: Nikon D7000 Dynamic Range
Post by: JR on December 12, 2010, 08:11:14 am

Bill,

Conclusion from Roger Clark:
Current good quality sensors in digital cameras are photon noise limited. This means there is no possible improvement in performance for the high signal region (bright things in an image) except to increase quantum efficiency of the devices and/or the fractional active area for which the sensor converts photons to electrons (called the fill factor). As both of these properties are reasonably high already, there is limited room for improvement. And even if these properties were improved, there would still be a big difference between large and small pixels. Larger pixels have higher signal-to-noise ratio at all levels, but especially at low signal levels. The obvious improvement still possible would be to reduce the read noise, but that would likely improve large sensors also, thus large sensors with large pixels will always have an advantage.

What he is saying is interesting. We have not seen much of an improvement in capturing highlights. HTP, Active D-Lightning etc are only in-camera manipulations. The Fuji S5 Pro is the only camera using new technology in this area.

But we have seen  improvements in read-noise at low signal levels. The new Sony made sensor we are discussing here is an example. It will be interesting to see if this will benefit future full-frame sensors from Nikon or hopefully Canon?

- John


See Roger Clark's essay (http://www.clarkvision.com/articles//does.pixel.size.matter/#Example_Noise).

Regards,

Bill
Title: Re: Nikon D7000 Dynamic Range
Post by: bjanes on December 12, 2010, 08:46:57 am
Conclusion from Roger Clark:

And even if these properties were improved, there would still be a big difference between large and small pixels. Larger pixels have higher signal-to-noise ratio at all levels, but especially at low signal levels. The obvious improvement still possible would be to reduce the read noise, but that would likely improve large sensors also, thus large sensors with large pixels will always have an advantage. [/i]

But we have seen  improvements in read-noise at low signal levels. The new Sony made sensor we are discussing here is an example. It will be interesting to see if this will benefit future full-frame sensors from Nikon or hopefully Canon?

John,

I don't follow Canon that closely, but Nikon has already made considerable progress in improving the read noise for their full frame sensors. Look at the following DR plot for the D7000, D3x and D3 as determined by DXO. I choose to use the screen mode to look at per pixel performance. The D3 curve flattens to the left due to excessive read noise, whereas the D3x exhibits less flattening, and the D7000 practically none. For a tutorial on reading the DXO DR plot, see Emil Martinec (http://www.luminous-landscape.com/forum/index.php?topic=42158.msg352373#msg352373).

Regards,

Bill
Title: Re: Nikon D7000 Dynamic Range
Post by: JR on December 12, 2010, 09:11:03 am

Bill,

I have not read Emil´s tutorial  yet but I will.

As a Canon user I have to agree that Nikon have made huge improvements in regards to lower the read noise. I don´t think Canon´s sensor performs bad, but I do think they have fallen behind a bit. If they don´t keep up with Nikon/Sony with their next releases in 2011 I think they will fall further behind in this respect.

- John

John,

I don't follow Canon that closely, but Nikon has already made considerable improvement in improving the read noise for their full frame sensors. Look at the following DR plot for the D7000, D3x and D3 as determined by DXO. I choose to use the screen mode to look at per pixel performance. The D3 curve flattens to the left due to excessive read noise, whereas the D3x exhibits less flattening, and the D7000 practically none. For a tutorial on reading the DXO DR plot, see Emil Martinec (http://www.luminous-landscape.com/forum/index.php?topic=42158.msg352373#msg352373).

Regards,

Bill
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 12, 2010, 07:26:48 pm

At 0.1% grey ( logarithmic scale ) the SNR is ca 16dB for the D7000. The 50D´s SNR is just above 6dB. That is very low. What do you think? Would you consider 6dB deep shadows?


John,
I think this point needs further clarification. What is deep shadow is what the eye perceives as deep shadow, bearing in mind that the aperture of the eye, the pupil, is constantly changing according to the changing levels of reflected light within the scene, as the eye peruses the scene.

If the eye had a fixed aperture like a camera does at the moment the shot is taken, we'd be in deep trouble. We'd be blinded by even moderately bright light, and even moderately dark shadows would appear impenetrably black.

So the answer is, a signal level which is only 6dB above the noise floor of the camera can be representative of a deep shadow in a scene, especially if the scene is of low contrast and low dynamic range. On the other hand, if the scene is of high dynamic range, a shadow which the eye perceives as normal shade where the light is more than sufficient to read a book easily, may appear in the camera's sensor, and consequently in the processed image, as a deep, noisy shadow with a 6dB SNR or less, which has to be rendered black.

Now, I know it's the case that the sun was last seen in Great Britain in the afternoon of the 23rd of August 1955 (well, let's not exaggerate. I think it might have been seen on a few occasions  since then), and I was informed recently by a tourist guide that St Petersburg gets on average about 65 sunny days per year, so I considered myself lucky that the sun was shining for 2 out of the 4 days I was there.

So, for the benefit all the sunshine-deprived people who might never have seen a 'high dynamic range' scene, I searched through some shots I'd taken with my 5D of the temples at Siem Riep in Cambodia, back in 2006, looking for an example with shade which was not at all deep, in which the light was perfectly adequate for reading a book, but which the camera simply cannot render as the eye saw it, because of the camera's limited dynamic range.

Here's that shot which is totally useless because of noisy shadows. The sky and clouds are okay though.

First the ACR Window demonstrating that the shot is a reasonable ETTR, followed by a crop of the sky showing good detail in the clouds.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on December 12, 2010, 07:43:42 pm
Let's now have a look at some shadows, not deep shadows, but merely areas in the shade under a tree.

Phwoar! What subtle detail and texture in that laterite stone. Can you see it?  ;D

I certainly could at the time, when I was there.
Title: where deep shadows begin? depends on desired "tonal placement" in the print
Post by: BJL on December 12, 2010, 10:37:12 pm
I think we have to ask DxoMark if we want to know exactly where the deep shadows begin.
I think the answer depends on what in the Zone System is called your choice of "placement": at what brightness level you intend to print (or otherwise present) subject matter that is at a certain brightness level in the scene. Sometimes, there could be a shaded subject that is only 1% as bright as another, sunlit, part of the scene and you wish to place that shaded subject in the print as only a stop or so below middle gray ... at the cost of greatly reducing the relative brightness level at which the sunlit parts are placed on the print. Maybe ranges even more extreme than 100:1 can occur between, say, (a) shaded leaves or rocks that one wants to rendered light enough to show details, so not much more than one stop darker than middle gray, and (b) sunlit clouds or snow that one does not want rendered as sterile blank white, which on a print means not more than three stops lighter than middle gray. But slides and computer screens can go far brighter with the highlights than light reflected of a paper print.
Title: Re: Nikon D7000 Dynamic Range
Post by: thierrylegros396 on December 13, 2010, 03:10:41 am
To futher improve DR, may we imagine ISO25 based sensors ?!

Thierry
Title: Re: Nikon D7000 Dynamic Range
Post by: PierreVandevenne on December 13, 2010, 11:43:37 am
To futher improve DR, may we imagine ISO25 based sensors ?!

At the risk of repeating what's been said before: sensors don't have ISO values or base ISOs. They count photons. The more photons they can count (well capacity), the better it is for DR. The more the count is precise (in other words, the less noise of all source is present), the better it is for DR. That's all there is to it at the bottom with the current technology.  In that respect, the Sony sensor is clearly a winner, most probably if one reads Sony's tech papers and patent because a tremendous amount of work has been done on sensel measuring accuracy. They seem to have, at the sensel level, a processing that is more complex than what was done on a full frame basis by scientific sensors not so long ago.

The rest is just the result of some interpretation of the (true) RAW data by the camera hardware and firmware, normalized for the photographer's comfort. This is of course very important from the photographer's point of view, and there are advantages in knowing which abstract normalized setting (ISO) is best for a specific camera. But making the sensor-camera system better at an ISO value or another doesn't fundamentally change the situation.
Title: Re: Nikon D7000 Dynamic Range
Post by: thierrylegros396 on December 13, 2010, 03:42:01 pm
OK, understood , well described !

What is really interresting in the D7000 and K5 cases is how they achieve the 3dB/stop slope !

Passive or active circuit ?!
Title: Re: Nikon D7000 Dynamic Range
Post by: JR on December 14, 2010, 09:26:00 am

So the answer is, a signal level which is only 6dB above the noise floor of the camera can be representative of a deep shadow in a scene...


Finally we agree  ;D

Seriously, I understand what you mean.. everything is relative.






Now, I know it's the case that the sun was last seen in Great Britain in the afternoon of the 23rd of August 1955 (well, let's not exaggerate. I think it might have been seen on a few occasions  since then)


Two or three occasions, that´s right.

 

Title: Re: Nikon D7000 Dynamic Range
Post by: JR on December 14, 2010, 09:40:27 am
Let's now have a look at some shadows, not deep shadows, but merely areas in the shade under a tree.

Phwoar! What subtle detail and texture in that laterite stone. Can you see it?  ;D

I certainly could at the time, when I was there.


That´s right. Everything in life is relative. DR too. And shadows  ;)

What would be your estimate for this scene in terms of DR?

Nice pictures by the way. I like old trees.

The noise in the shadows has Canon trademarks all over it. I was using the D700 for a while earlier this year and I had to push the shadows really hard to get the same kind of noise I got from my Canon´s with no post processing in contrasty scenes.

How do you like the D7000 so far?


- John
Title: Re: where deep shadows begin? depends on desired "tonal placement" in the print
Post by: JR on December 14, 2010, 10:01:31 am
I think the answer depends on what in the Zone System is called your choice of "placement": at what brightness level you intend to print (or otherwise present) subject matter that is at a certain brightness level in the scene. Sometimes, there could be a shaded subject that is only 1% as bright as another, sunlit, part of the scene and you wish to place that shaded subject in the print as only a stop or so below middle gray ... at the cost of greatly reducing the relative brightness level at which the sunlit parts are placed on the print. Maybe ranges even more extreme than 100:1 can occur between, say, (a) shaded leaves or rocks that one wants to rendered light enough to show details, so not much more than one stop darker than middle gray, and (b) sunlit clouds or snow that one does not want rendered as sterile blank white, which on a print means not more than three stops lighter than middle gray. But slides and computer screens can go far brighter with the highlights than light reflected of a paper print.

BJL,

That is true. Choice of placement is important. A digression... When I work on images I use Photoshop tools like dodge&burn a lot on my B&W prints. Used carefully they can give the impression of higher DR in a print.  There is of course no real substitute for "choice of placement" and proper exposure but I find tools like d&b very useful. Knowing exactly where to place the shadows, mid-tones etc when you do the exposure is an art-form I think.

- John

 
Title: Re: Nikon D7000 Dynamic Range
Post by: bjanes on December 14, 2010, 05:49:23 pm
At the risk of repeating what's been said before: sensors don't have ISO values or base ISOs. They count photons. The more photons they can count (well capacity)...

I take exception to both of these statements. ISO 12232:2006 defines how the sensors in digital still cameras are rated. For a good summary, see this article (http://en.wikipedia.org/wiki/Film_speed) on Wikipedia. The ISO saturation rating is used by DXO (http://www.dxomark.com/index.php/en/Learn-more/DxOMark-database/Measurements/ISO-sensitivity).

Most digital sensors do not have the resolution to count individual photons. Rather, the photons generate a charge or voltage, which is analog and is converted to a data number by the ADC (analog to digital converter). The number of photons collected is related to the data number by the camera gain (photo electrons per data number).

Regards,

Bill
Title: Re: Nikon D7000 Dynamic Range
Post by: PierreVandevenne on December 15, 2010, 07:12:24 am
Yes, there is a "rating" in ISO for sensors. But that doesn't mean engineers sit down and design a 50 or 400 ISO sensor or that building a "25 ISO sensor" is the way to go to improve quality. It is just a _rating_, a bit like a credit rating, that is used to describe a certain behaviour in a way that is palatable for photographers. A far as photon counting is concerned, we can of course nitpick and, usualy, I think in terms of ADU (essentially because I used CCDs before they appeared in cameras) so I am well aware that we are not necessarily counting individual photons (but we aren't too far either) and that we aren't counting them perfectly either: in fact, we are counting them  with a coarse resolution.

This being said while all these notions of stops/ISO/photographic DR are certainly useful they do obfuscate the issues. That probably explains why we have seen outlandish claims in terms of DR which are simply impossible given a specific well capacity, even if the system was a perfect noiseless photon counter. I've been toying with a small sensor simulator that I wrote to try to reproduce the behaviour of camera sensors and I am under the impression that a lot of massaging is going on in the background. One possibility to extend the DR, at least in a photographic context, would be to have sensors with variable pixel gain.

At some point, I can see that converging with software HDR and changing our expectations about how images should look.

Title: Re: Nikon D7000 Dynamic Range
Post by: thierrylegros396 on December 15, 2010, 07:55:18 am

One possibility to extend the DR, at least in a photographic context, would be to have sensors with variable pixel gain.


Could it be possible that K5 and D7000 are working with such a sensor ?!
Title: Re: Nikon D7000 Dynamic Range
Post by: bjanes on December 15, 2010, 08:59:32 am
Yes, there is a "rating" in ISO for sensors. But that doesn't mean engineers sit down and design a 50 or 400 ISO sensor or that building a "25 ISO sensor" is the way to go to improve quality. It is just a _rating_, a bit like a credit rating, that is used to describe a certain behaviour in a way that is palatable for photographers. A far as photon counting is concerned, we can of course nitpick and, usualy, I think in terms of ADU (essentially because I used CCDs before they appeared in cameras) so I am well aware that we are not necessarily counting individual photons (but we aren't too far either) and that we aren't counting them perfectly either: in fact, we are counting them  with a coarse resolution.

No one said that an engineer sits down and designs an ISO 40 or 400 sensor. The ISO rating merely allows one to determine how the sensor will respond to a given exposure, measured in lux*seconds. The analogy of a credit score is a poor one, since the credit score is largely determined by past behavior. If the creditor loses his job or incurs large medical bills, his behavior may change, but the behavior of the sensor is determined by the laws of physics. If you expose a uniformly lit surface according to a TTL light meter reading, the sensor will receive a predetermined exposure (lumens/square meter * seconds). Roger Clark (http://www.clarkvision.com/imagedetail/digital.photons.and.qe/index.html) gives equations for converting to incident photons. How many of those photons are captured as photoelectrons depends on the performance of the microlenses, absorption by the Bayer filters, quantum efficiency and other factors. I agree we are counting photons in a general way.

The ISO rating of the sensor is a very useful entity. If we expose according to the meter reading with a camera using the ISO saturation rating for the sensor and standard ISO calibration for the meter, the sensor will attain approximately 12.5% saturation. If we increase the exposure by 3 EV, the sensor will be at saturation. This relationship is helpful in exposing the highlights in ETTR.

Many camera manufacturers do not use the ISO saturation standard, but one can obtain the saturation ISO from DXO. The actual ISO is usually not the nominal (stated ISO). I would imagine that an engineer would design a sensor for optimal overall performance rather than to a predetermined ISO rating. The ISO rating would then be rounded to the nearest standard ISO number.

Regards,

Bill

Title: Re: Nikon D7000 Dynamic Range
Post by: PierreVandevenne on December 15, 2010, 09:44:41 am
Quote
No one said that an engineer sits down and designs an ISO 40 or 400 sensor

Well, that was essentially the message I was responding to. But I don't see this in a confrontational way.

Quote
The ISO rating of the sensor is a very useful entity.

For photography practice, I agree, just like other abstractions are.  But I don't think they are helpful as far as getting to the bottom of things.
Just take a very simple case such as the focal length issue. Thinking in terms of 35mm equivalent has led to mass confusion in the early days of digital. Think in terms of what focal length means and size of sensors and the issue becomes 6th grade level. Of course, marketing wise it was better to claim an "38-380 mm focal length lens" in a small package than to claim having a "super cropping sensor". The same happens here, but there are so many factors that it is even more confusing.

Title: Re: Nikon D7000 Dynamic Range
Post by: hjulenissen on December 17, 2010, 03:26:58 am
I am a big fan of graphical representations of complex matters.

Even though my physics may be wrong, do you think that the fundamental idea behind the plot included could be used as a means to convey and discuss DR/noise/linearity aspects of a sensor and camera?
Title: Re: Nikon D7000 Dynamic Range
Post by: dosdan on March 19, 2011, 02:03:29 am
A generic comment on DR. I really think that the discussion around DR is overblown. Much of the discussion at all is overblown.

My experience is that DR is essentially plentiful when shooting with present days DSLRs at base ISO correctly exposing to the right. In real life we always have lens flare that reduces the achievable DR anyway.

There has been some discussion that a 13-stop or 14-stop DR is meaningless in the real world because of lens flare.  So instead consider the DxOMark SNR 18% figures both within and between formats. To my way of thinking, this is a reasonable indicator of how well the sensors in the cameras are performing for their size.

SNR 18% comparison within and between formats
 (http://www.pentaxforums.com/forums/photography-articles/129754-comparison-snr-18%25-across-formats.html)

Dan.



Title: Re: Nikon D7000 Dynamic Range
Post by: bluekorn on March 20, 2011, 03:18:43 pm
The DR of my ability to comprehend the technical delights involved in this discussion moved far beyond the right hand edge of my cerebral histogram during my reading in the first three of four pages here. Without wading through the remaining pages I'm going to put my IQ at risk and interject a beginners question.

I frequently find myself shooting Lake Superior scenes that include 2 to 2 1/2 stops of soft fog twilight that can be moved left to right, or right to left, presumably capturing the full dynamic range of the scene at many points along the histogram. The perceived optimal image on the LCD often appears "correct" to my eye at the histogram midpoint or even to the left of midpoint. When the appearance of a darker image with limited DR is desired for aesthetic reasons do we still shoot to the right ensuring well saturation and then somehow find our way back to apparent lower light levels in post processing?

Peter
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on March 21, 2011, 11:04:00 am
The DR of my ability to comprehend the technical delights involved in this discussion moved far beyond the right hand edge of my cerebral histogram during my reading in the first three of four pages here. Without wading through the remaining pages I'm going to put my IQ at risk and interject a beginners question.

I frequently find myself shooting Lake Superior scenes that include 2 to 2 1/2 stops of soft fog twilight that can be moved left to right, or right to left, presumably capturing the full dynamic range of the scene at many points along the histogram. The perceived optimal image on the LCD often appears "correct" to my eye at the histogram midpoint or even to the left of midpoint. When the appearance of a darker image with limited DR is desired for aesthetic reasons do we still shoot to the right ensuring well saturation and then somehow find our way back to apparent lower light levels in post processing?

Peter


This topic of ETTR seems inexaustible.

The problem of attempting an accurate ETTR, in my experience, is the problem of inadvertantly blowing at least one channel in the brightest parts of the image.

If you have the luxury of time on your side, you can adopt the technique of using the spot meter mode on the brightest part of the image, then in manual mode increase exposure by an experimentally determined number of stops. For the Canon 5D, as I recall, that was 3 stops slower than the spot meter reading directed at the brightest part of the scene.

I gave up this technicque because it was too time-consuming and I missed a few moments, but I was impressed with its accuracy.

To avoid missing the moment, I now prefer to auto-bracket exposure when the scene has a high range of brightness levels.

Clearly, if the scene does not have a wide range of brightness levels, and you are using a camera that does have a wide dynamic range, such as the D7000, then it's not worth stressing yourself about getting an ETTR  (the purpose of which is to lower noise in the shadows and lower midtones) unless you are using a high ISO for the need of a fast shutter speed.

At high ISO, say 800 or 1600 and above, the DR of the camera is significantly reduced. For clean midtones, an ETTR is essential in those circumstances.

If in doubt, experiment with auto-bracketing +/- 1 stop.
Title: Re: Nikon D7000 Dynamic Range
Post by: bluekorn on March 21, 2011, 03:25:02 pm
Ray, thank you. This is very helpful. The behavior of digital cameras from capture through processing to card storage is very complex to my way of thinking. I find it challenging to ferret out the rudimentary understanding, which is my need and want, from the body of scientific discussions which quite naturally diverge into seemingly endless channels of nuance beyond my interest and ability. And I agree with you that some notion of how it all works and the ability to keep from making the same mistakes twice, the improved efficiency in process, adds considerably to the pleasure in making photographs. Thanks again. Peter 
Title: Re: Nikon D7000 Dynamic Range
Post by: bjanes on March 22, 2011, 11:28:07 am

Clearly, if the scene does not have a wide range of brightness levels, and you are using a camera that does have a wide dynamic range, such as the D7000, then it's not worth stressing yourself about getting an ETTR  (the purpose of which is to lower noise in the shadows and lower midtones) unless you are using a high ISO for the need of a fast shutter speed.

At high ISO, say 800 or 1600 and above, the DR of the camera is significantly reduced. For clean midtones, an ETTR is essential in those circumstances.

I agree that if one has a camera with low read noise and a high DR (such as the Nikon D7000), obtaining a perfect ETTR is not necessary since one might blow the highlights and lose data. However, the concept of ETTR implies that a histogram to the right is the critical factor, whereas in fact the exposure (number of photons collected) is the critical factor. Older cameras such as the Nikon D3 have higher read noise at low ISO, and when f/stop and shutter speed considerations limit exposure, it is advantageous to increase the ISO to take advantage of the lower read noise.

However, read noise approaches a minimum asymptotically at higher ISO, and raising the ISO beyond this point only serves to limit head room without decreasing read noise. As Emil Martinec has pointed out, this point of diminishing returns can be determined by looking at the DR plotted vs the ISO on DXO. In a camera whose DR is limited by shot noise, the plot becomes linear and DR drops by one stop for each doubling of ISO.  When read noise is significant, the curve bows downward towards the left, as shown for the D3 plot below ISO 800.

As the plot shown below indicates, the curve for the D3 becomes linear slightly below ISO 800. Increasing ISO above 800 with this camera limits highlight headroom and does nothing for the shadows; one can leave the camera setting at 800 and merely increase exposure in the raw converter. If the histogram is to the left at ISO 1600 and to the right at ISO 800, the DR will be similar, but with ISO 1600 there is a danger of blowing the highlights. In this sense, ETTR judged by the histogram is really a misnomer.

The D7000 is linear from the start, and one really does not have to increase the ISO to obtain a better read noise. One could leave the ISO setting at base and give as much exposure as f/stop and shutter speed concerns allow, and then increase exposure in the raw converter. Of course, the image will appear dark on the camera LCD, but highlight head room will be preserved.

Regards,

Bill




Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on March 22, 2011, 04:00:45 pm

The D7000 is linear from the start, and one really does not have to increase the ISO to obtain a better read noise. One could leave the ISO setting at base and give as much exposure as f/stop and shutter speed concerns allow, and then increase exposure in the raw converter. Of course, the image will appear dark on the camera LCD, but highlight head room will be preserved.

Regards,

Bill


That's quite true, Bill. I was really speaking in general terms in my previous post. It's not clear that Bluekorn uses a D7000.

The D7000 is in a special category that makes the concept of ETTR quite redundant when the shutter speed at base ISO, required for an ETTR, is too slow for the subject, or too slow to prevent camera shake.

Having determined that the shutter speed at base ISO necessary for a reasonably accurate ETTR is too slow for the circumstances, one can simply switch to manual mode (if one isn't already in manual mode) and increase the shutter speed to whatever one assesses is appropriate, without bothering to change ISO.  ETTR is then no longer a consideration and one doesn't have to worry about the possibility of blown highlights.
Title: Re: Nikon D7000 Dynamic Range
Post by: bluekorn on March 22, 2011, 08:27:55 pm
I presently shoot with a Sony R1 but in in order to avoid further graduate studies I'm considering buying the D7000 as it "is in a special category that makes the concept of ETTR quite redundant" (thank you Ray).

The "number of photons collected" is the critical factor. (In fact, I feel an intuitive resonance with this claim although I couldn't support it logically). I recall reading somewhere that the further right one goes on the histogram the greater the number of photons one will collect. The author divided the histogram into thirds and stated in support of ETTR that something like sixty percent of photons collected are available to the right hand third and only ten percent in the left hand third. I drew from this that even though the DR of many of the subjects I shoot is two to two and a half stops, I would benefit from ETTR because I collected more photons. I'm certainly over my head in this discussion but I sincerely want to capture photons to my best advantage in making prints.



 
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on March 23, 2011, 03:27:42 am

The "number of photons collected" is the critical factor. (In fact, I feel an intuitive resonance with this claim although I couldn't support it logically). I recall reading somewhere that the further right one goes on the histogram the greater the number of photons one will collect. The author divided the histogram into thirds and stated in support of ETTR that something like sixty percent of photons collected are available to the right hand third and only ten percent in the left hand third. I drew from this that even though the DR of many of the subjects I shoot is two to two and a half stops, I would benefit from ETTR because I collected more photons. I'm certainly over my head in this discussion but I sincerely want to capture photons to my best advantage in making prints.


For the smoothest and cleanest image the camera is capable of, one should ideally strive to capture as many photons as possible, consistent with an oppropriate shutter speed and aperture, and without blowing any of the channels.

However, there are lots of trade-offs and compromises on the technical side of photography that one has to deal with when the camera is not used in fully automatic mode, so one should try to  be aware of the significance of the effects of any settings which may not be ideal as a result of the requirements for the circumstances and the lighting conditions.

That is why I recommend experimenting with different settings, different exposures through autobracketing for example, to see for oneself what effect an underexposure of 1/2 a stop, or 1 stop, or 2 stops or more, may have on the quality of certain parts of an image using a particular model of camera.

Because I'm a peripatetic type of photographer, I don't always have the time to prepare each shot for a perfect ETTR, nor the opportunity to retake the same scene if I got it wrong, so I'm very attracted to the high-DR characteristics of the D7000 which allow me to underexpose an image at base ISO by at least one stop, and maybe as much as 2 stops, whether by design or accident, and still achieve image quality in the shadows on a par with an ETTR shot of the same scene using the equivalent Canon 60D.

Comparing the D7000 at 1 stop underexposure with the 60D at half the shutter speed (double the exposure), I would not expect to see any image quality advantage in the 60D image in any respect, whether in the deep shadows, moderate shadows, midtones or highlights, with regard to DR, SNR, tonal range or color sensitivity. Slight differences in resolution due to lens quality, AA filter characteristics and sensor pixel count is another issue.

A two-stop underexposure comparison would be interesting because theoretically shot noise in the shadows of the D7000 image should then be greater, and SNR in the midtones might also be noticeably worse.

On the other hand, the advantages of a 1/100th sec exposure with the D7000, as opposed to a 1/25th sec exposure with the 60D, could be of far greater benefit than the disadvantage of a barely perceptible increase in shot noise or a barely perceptible reduction in SNR in the midtones that might only be apparent at 100% on the computer monitor, representative of a huge print of around 6ftx4ft.

Title: Re: Nikon D7000 Dynamic Range
Post by: hjulenissen on March 23, 2011, 02:09:51 pm
On the other hand, the advantages of a 1/100th sec exposure with the D7000, as opposed to a 1/25th sec exposure with the 60D, could be of far greater benefit than the disadvantage of a barely perceptible increase in shot noise or a barely perceptible reduction in SNR in the midtones that might only be apparent at 100% on the computer monitor, representative of a huge print of around 6ftx4ft.
I agree that having a larger practical DR is a significant recent progress in DSLRs. If not for carefully planned studio-shots of sensible DR scenes, then for practical photography where you have one chance to get it right, and light can be hard to control.

But if the differences in noise are none between a D7000@1/50s and a 60D@1/25s and "barely perceptible" between a D7000@1/100s and a 60D@1/25s, would you not also expect the differences to be "barely perceptible" between a 60D@1/25s and a 60D@1/50s?

I agree that capturing a large amount of photons is important. I am sceptical about the implicit message that perceptual image quality is somehow a 1:1 correlate with the number of counted photons. Clearly it is not, as very few photons are needed to distinguish one scene from another (say, 100 photons per pixel on average), while increasing the average number of photons per pixel from 100000 to 100100 will make no perceptual difference at all. Stephens power law etc.

-h
Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on March 24, 2011, 02:31:10 am
Hi!

I don't understand the reasoning about ETTR. ETTR just says that we want maximum exposure without clipping non specular highlights. This essentially means that we are maximizing the number of photons detected. I can see there can be problems with the histogram representation, but would we have a "raw" histogram I would expect a correctly ETTR image to have maximum possible exposure.

Best regards
Erik


I agree that if one has a camera with low read noise and a high DR (such as the Nikon D7000), obtaining a perfect ETTR is not necessary since one might blow the highlights and lose data. However, the concept of ETTR implies that a histogram to the right is the critical factor, whereas in fact the exposure (number of photons collected) is the critical factor. Older cameras such as the Nikon D3 have higher read noise at low ISO, and when f/stop and shutter speed considerations limit exposure, it is advantageous to increase the ISO to take advantage of the lower read noise.

However, read noise approaches a minimum asymptotically at higher ISO, and raising the ISO beyond this point only serves to limit head room without decreasing read noise. As Emil Martinec has pointed out, this point of diminishing returns can be determined by looking at the DR plotted vs the ISO on DXO. In a camera whose DR is limited by shot noise, the plot becomes linear and DR drops by one stop for each doubling of ISO.  When read noise is significant, the curve bows downward towards the left, as shown for the D3 plot below ISO 800.

As the plot shown below indicates, the curve for the D3 becomes linear slightly below ISO 800. Increasing ISO above 800 with this camera limits highlight headroom and does nothing for the shadows; one can leave the camera setting at 800 and merely increase exposure in the raw converter. If the histogram is to the left at ISO 1600 and to the right at ISO 800, the DR will be similar, but with ISO 1600 there is a danger of blowing the highlights. In this sense, ETTR judged by the histogram is really a misnomer.

The D7000 is linear from the start, and one really does not have to increase the ISO to obtain a better read noise. One could leave the ISO setting at base and give as much exposure as f/stop and shutter speed concerns allow, and then increase exposure in the raw converter. Of course, the image will appear dark on the camera LCD, but highlight head room will be preserved.

Regards,

Bill





Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on March 24, 2011, 10:15:55 am
Hi!

I don't understand the reasoning about ETTR. ETTR just says that we want maximum exposure without clipping non specular highlights. This essentially means that we are maximizing the number of photons detected. I can see there can be problems with the histogram representation, but would we have a "raw" histogram I would expect a correctly ETTR image to have maximum possible exposure.

Best regards
Erik



Erik,
If ETTR essentially means maximising the number of photons detected (without clipping non-specular highlights) then ETTR is only possible at base ISO. Any exposure at a higher-than-base ISO, which does not result in a clipping of highlights, is an underexposure which has been amplified in-camera to a degree specified by the ISO setting.

To put it another way, any ISO setting above base ISO is an instruction to the camera to treat the signal as though it is an underexposure and to apply the appropriate degree of amplification in accordance with those instructions.

As you know, it's long been recognised with Canon and Nikon cameras that such amplification has advantages with regard to SNR because the amplification takes place before A/D conversion so that all further processing up-chain is effectively of a signal which is no longer underexposed.

Such an amplified signal will inevitably contain more noise than an ETTR exposure at base ISO, but the additional noise introduced as the signal is processed in-camera, starting with the A/D conversion, will have no more of an adverse effect on SNR than it would have had if the signal had been an ETTR at base ISO.

The consequence of this approach is that an ETTR exposure at ISO 200 has a better SNR than the same exposure at ISO 100, with most Canon and Nikon cameras.

The D7000 and Pentax K5 seem to have broken with this tradition. Unless you want a nice-looking review on the camera's LCD screen to show off the shot you've just taken of the nice-looking lady, it's probably better to underexpose 1 stop at base ISO than attempt an ETTR  at ISO 200, or underexpose 2 stops at ISO 100 than attempt an ETTR at ISO 400 etc, etc.

The advantage of this different technique with the D7000 is that there's no danger of blowing highlights but also no disadvantage of getting a worse SNR than one might have got using an ETTR at the appropriately higher ISO in relation to the same shutter speed and aperture.

Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on March 24, 2011, 10:27:16 am

But if the differences in noise are none between a D7000@1/50s and a 60D@1/25s and "barely perceptible" between a D7000@1/100s and a 60D@1/25s, would you not also expect the differences to be "barely perceptible" between a 60D@1/25s and a 60D@1/50s?


Not necessarily. If you double the number of photons collected, using the same camera, the noise in absolute terms can never be less. In fact it has to be at least marginally more. Photonic shot noise increases with increasing photon count, and read noise is also slightly greater with a greater signal.

What's important is the amount of noise in relation to the amount of signal, ie. signal-to-noise ratio. The D7000 produces less than half the noise in absolute terms as the D60 produces with twice the signal or twice the photon count, at base ISO.
Title: Re: Nikon D7000 Dynamic Range
Post by: JR on March 24, 2011, 03:13:17 pm

As you know, it's long been recognised with Canon and Nikon cameras that such amplification has advantages with regard to SNR because the amplification takes place before A/D conversion..
 

This is a sidetrack but....

Do you know if Canon`s DIGIC 4 processor is involved in removing noise from raw files? I know it is treating JPEG`S. Not sure about raw files.

In this article http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=1407 Canon is talking about their DIGIC 4 processor.

Quote from the section named "Canon Digital Photo Professional software" : However, while DPP can read the camera settings in effect at the time the images are taken, it tends to downplay the effect of the camera’s High ISO Noise Reduction. You may see little difference if you compare two RAW files, one with NR active, and one with it turned off.

Quote from summary: "It has a noticeable impact on the level of visible noise in shots taken at higher ISO levels, and can even have a positive effect on an image at lower ISOs....For RAW shooters, it can also make a noticeable difference in how Canon's software processes your images -- although with Digital Photo Professional software, you're free to independently adjust chrominance and luminance noise reduction beyond the initial in-camera settings."

I have never shot raw with NR turned on. From the article it seems like there is some work done to the raw file by the DIGIC 4 processor but perhaps it is so insignificant that it is difficult to see?


- John
Title: Re: Nikon D7000 Dynamic Range
Post by: BernardLanguillier on March 24, 2011, 08:25:43 pm
Do you know if Canon`s DIGIC 4 processor is involved in removing noise from raw files? I know it is treating JPEG`S. Not sure about raw files.

I believe that all cameras do some form of signal processing when converting the analog current coming out of the sensor to bits. That goes for DSLRs and digital backs.

I am not sure what the old myths is based on that some brands do less of that which results in better raw files. The good folks at Pentax where for sure explaining to me that the quality of their processing they apply to their files explains the very low amount of moire that can be seen in the 645D dng.

Let's face it, we don't really want to know what comes out of a sensor and real raw data isn't really available to anyone but the engineers developing cameras. :)

Cheers,
Bernard
Title: Re: Nikon D7000 Dynamic Range
Post by: dosdan on March 24, 2011, 09:35:06 pm
I recall reading somewhere that the further right one goes on the histogram the greater the number of photons one will collect.


Only at base ISO.

 
Dan.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on March 25, 2011, 02:07:46 am

Only at base ISO.

 
Dan.

That doesn't sound right, does it!

The further right one goes on the histogram, whatever the ISO setting, the more photons will be collected. However, if one wishes to maximise the number of photons the sensor is capable of collecting, one must be at base ISO.
Title: Re: Nikon D7000 Dynamic Range
Post by: PierreVandevenne on March 25, 2011, 05:25:07 am
I am not sure what the old myths is based on that some brands do less of that which results in better raw files.

I think it is mostly based on very low light imaging, such as astonomical imaging. Canon's RAW files were much closer to what people expected from scientific based CCDs and yielded better results after a complete standard processing pipe-line. Nikon had a tendency of "eating" stars and dropping very faint signals (to cut a long story short). Of course, that type of imaging isn't totally congruent with normal photography needs where the goal is more "no visible noise in deep shadows" rather than "see these tiny details in the noise".

While reality is intrinsically noisy, we don't want to know about it and almost always prefer visual smoothness.
Title: Re: Nikon D7000 Dynamic Range
Post by: Ray on March 27, 2011, 01:49:11 am
I think it is mostly based on very low light imaging, such as astonomical imaging. Canon's RAW files were much closer to what people expected from scientific based CCDs and yielded better results after a complete standard processing pipe-line. Nikon had a tendency of "eating" stars and dropping very faint signals (to cut a long story short). Of course, that type of imaging isn't totally congruent with normal photography needs where the goal is more "no visible noise in deep shadows" rather than "see these tiny details in the noise".

While reality is intrinsically noisy, we don't want to know about it and almost always prefer visual smoothness.

Yes, I believe that's the case. With the D7000 one can underexpose a shot, say at night, by 6 stops or more at base ISO, and when one reviews the image in ACR the screen can be totally black, initially.

One then hits the 'auto' button and the entire scene springs to life.

It's noisy of course, as one would expect any shot at ISO 6400 or 128,000 to be noisy, but the image still retains convincing blacks. There seems to be a clipping point for blacks which doesn't exist in Canon DSLR images.

The underexposed deep shadows in a Canon RAW  image seem to contain all the objectionable banding and pattern noise which gets progressively worse the deeper the shadow or the greater the underexposure.

Such an effect can be quite interesting, particularly from the 5D, if one is trying to create a semi-abstract photograph that looks like a tapestry woven from a coarse, reddish thread.  ;D
Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on March 30, 2011, 12:52:06 am
Hi,

I'd suggest that you are wrong on this. Increasing exposure will always increase the numbers of photons collected, independent of ISO.

But, we deserve better histograms (actually showing sensor signal and not processed data).

Best regards
Erik


Only at base ISO.

 
Dan.
Title: Re: Nikon D7000 Dynamic Range
Post by: hjulenissen on March 30, 2011, 11:48:56 am
Hi,

I'd suggest that you are wrong on this. Increasing exposure will always increase the numbers of photons collected, independent of ISO.

But, we deserve better histograms (actually showing sensor signal and not processed data).

Best regards
Erik

If you keep everything else constant and increase the ISO, I think that the histogram will move to the right due to analog amplification, without changing the number of photons actually counted by the sensor?

-h
Title: Re: Nikon D7000 Dynamic Range
Post by: LKaven on March 30, 2011, 02:17:04 pm
If you keep everything else constant and increase the ISO, I think that the histogram will move to the right due to analog amplification, without changing the number of photons actually counted by the sensor?
I think this is what Erik is saying.  He'd like to see a histogram that reflects most accurately the numbers coming off the sensor.  As it is, we have to use things like UniWB to get the camera to approximate this.
Title: Re: Nikon D7000 Dynamic Range
Post by: hjulenissen on March 30, 2011, 02:50:46 pm
I think this is what Eric is saying.  He'd like to see a histogram that reflects most accurately the numbers coming off the sensor.  As it is, we have to use things like UniWB to get the camera to approximate this.
This is strange, indeed. If I use an audio-recorder, I expect its red/green LEDs to indicate clipping of its mic amplifier, A/D converter etc (usually, the clipping point of those should be close to each other, I think). I would not expect it to be tied in after automatic gain control, mp3 encoding etc. Why is photography any different?

My guess is that major camera manufacturers build their cameras mainly as jpeg cams. That is what a large part of their customers use, and it is easier to differentiate vs competitors on jpeg files than raw files. Therefore, the raw option is sort of an "added extra" for the nit-picking crowd.

I can see no technical reason why this is so difficult. What is UniWB, btw?

-h
Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on March 30, 2011, 03:16:38 pm
Hi!

http://www.guillermoluijk.com/tutorial/uniwb/index_en.htm

Best regards
Erik


I can see no technical reason why this is so difficult. What is UniWB, btw?

-h
Title: Re: Nikon D7000 Dynamic Range
Post by: LKaven on March 30, 2011, 08:31:45 pm
This is strange, indeed. If I use an audio-recorder, I expect its red/green LEDs to indicate clipping of its mic amplifier, A/D converter etc (usually, the clipping point of those should be close to each other, I think). I would not expect it to be tied in after automatic gain control, mp3 encoding etc. Why is photography any different?

My guess is that major camera manufacturers build their cameras mainly as jpeg cams. That is what a large part of their customers use, and it is easier to differentiate vs competitors on jpeg files than raw files.
I think you pretty much nailed it. 

In order to provide a preview on the camera's rear LCD, in most cases, the RAW data has to get passed through a JPG engine for rendering.  The histogram is generally derived from that. 
Title: Re: Nikon D7000 Dynamic Range
Post by: ErikKaffehr on March 30, 2011, 11:42:19 pm
Hi,

The RAW image itself is not really viewable, at minimum it needs to have a gamma curve, so some processing is needed, but I'd suggest that histogram should be based on raw data.

Anyone ride to see what happens if we overexpose at high ISO, do we get clipping?

Best regards
Erik


I think you pretty much nailed it. 

In order to provide a preview on the camera's rear LCD, in most cases, the RAW data has to get passed through a JPG engine for rendering.  The histogram is generally derived from that. 
Title: Re: Nikon D7000 Dynamic Range
Post by: douglasf13 on April 04, 2011, 11:43:16 am
Iliah Borg and Andrey Tverdokhleb contend that ETTR is mostly misguided with current DSLRs, and, once you start exposing midtones over a stop past midpoint, color starts to be negatively affected.
Title: Re: Nikon D7000 Dynamic Range
Post by: stamper on June 29, 2011, 04:52:43 am
Iliah Borg and Andrey Tverdokhleb contend that ETTR is mostly misguided with current DSLRs, and, once you start exposing midtones over a stop past midpoint, color starts to be negatively affected.

Half of the information from the camera is in the stop at the right hand side. If that hasn't been captured then it is a bigger problem than the one outlined by yourself, assuming that is .... it is a problem? There isn't a definitive answer to capturing all of the information available so you have to judge what is the lesser of the evils and exposing to the right makes sense.