interesting article

[RichardChang]

>Your contention that your camera back, which I take to be the Megavision E5, has no noise above Zone I is not credible.

You are right, and according to the included table, I stand corrected.

> In contrast to your statement that your camera is free of noise in Zone 10, the noise is actually greatest there, but because of the high S/N ration it is not evident.

Not evident is a critical concept.  Evident by what means?  I took a look at some of my images, specifically just brighter than zone I.  You are correct and because of your post, I went looking for noise and I did find a slight structure which became evident at 400% magnification.  It does not render on a print, even at 24x32", but it is there.  If I don't see the noise render, must I avoid the advantages I see in highlight tonality, just to remove an artifact that can't be seen?

>In view of this analysis, I think that your shots could benefit from exposure to the right.

I think the analysis, at least when based on the performance of the image when rendered on the output target, would suggest that I can choose the more important attribute as I see it; remove some noise that I cannot see on the print, or take the advantage of increased flexibility in crafting highlight detail upwards to the paper's highest separable value.  This careful examination of the noise you've alerted me to, has allowed me to eval the danger, and subsequently decide that it's not worth worrying about.

If you disagree, please inform us why the laws of physics do not apply to your camera.  

I do agree with the notion of ETTR, for lower s/n capture devices. The laws of physics do apply to our camera and you are correct to steer me back from the error of my claims.  I'll include your observation of the Kodak noise performance in my teaching, and I'll give you credit for alerting me to the perils of low valued noise.

Richard Chang

[bjanes]

> In contrast to your statement that your camera is free of noise in Zone 10, the noise is actually greatest there, but because of the high S/N ration it is not evident.

Not evident is a critical concept.  Evident by what means?  I took a look at some of my images, specifically just brighter than zone I.  You are correct and because of your post, I went looking for noise and I did find a slight structure which became evident at 400% magnification.  It does not render on a print, even at 24x32", but it is there.  If I don't see the noise render, must I avoid the advantages I see in highlight tonality, just to remove an artifact that can't be seen?

Richard Chang
[a href=\"index.php?act=findpost&pid=64251\"][{POST_SNAPBACK}][/a]

Richard,

Thank you for a gracious reply. The signal to noise ratio of a device capturing 100,000 electrons is absurdly high and far beyond 4 by 5 Velvia film. By not evident, I meant to the unaided human eye, which is the final arbiter of our photographic efforts. However, the digital S/N is progressively lower in the deep shadows and it is here that ETTR could help visually in Zone I as you noted. IMHO, use of base ISO can be more critical than ETTR for improved N/R.

[jani]

When is a camera's histogram available for viewing: before or after taking the shot?

After taking the shot, since it's showing the distribution of the number of pixels according to luminance (or red, green and blue channels) in the picture you just took (or to be specific, in the JPEG preview).

If a camera's histogram can display separate rgb channels, will you ETTR so that no channel is clipped?

If you don't want clipping, yes.

Of course, when in doubt, bracket, just like in the "good old" film days.

I think bracketing is overrated, since it requires that nothing is in motion.

Mountains and wind-free days are your friends.

The difference is burning storage rathen than film. How well do the higher end digital cameras support bracketing?

Canon isn't very good at automatic exposure bracketing, offering only +/- 3 EV in three steps. Recent Nikon cameras offer +/- 5 EV, if I recall correctly. But bracketing manually isn't that hard, if the scene allows you the time to do it.

[Chris_T]

After taking the shot, since it's showing the distribution of the number of pixels according to luminance (or red, green and blue channels) in the picture you just took (or to be specific, in the JPEG preview).
If you don't want clipping, yes.
I think bracketing is overrated, since it requires that nothing is in motion.

Mountains and wind-free days are your friends.
Canon isn't very good at automatic exposure bracketing, offering only +/- 3 EV in three steps. Recent Nikon cameras offer +/- 5 EV, if I recall correctly. But bracketing manually isn't that hard, if the scene allows you the time to do it.
[a href=\"index.php?act=findpost&pid=64263\"][{POST_SNAPBACK}][/a]

Some metering methods, such as spot metering, bracketing (a digital camera's long lag time between raw shots is a killer), etc., do not work well if the subjects within an image are not stationary, or if the lighting is constantly changing. ETTR is also in this category if the histogram is displayed after a shot.

[bjanes]

Some metering methods, such as spot metering, bracketing (a digital camera's long lag time between raw shots is a killer), etc., do not work well if the subjects within an image are not stationary, or if the lighting is constantly changing. ETTR is also in this category if the histogram is displayed after a shot.
[{POST_SNAPBACK}][/a]

Most cameras have a buffer that stores the shots while they are being processed and being written to the memory card. For example, in his tests of the Nikon D200 in DPReview, Phil noted that the camera could take 22 shots before slowing down. How much bracketing do you do?  

[a href=\"http://www.dpreview.com/reviews/nikond200/page12.asp]http://www.dpreview.com/reviews/nikond200/page12.asp[/url]

[Chris_T]

Most cameras have a buffer that stores the shots while they are being processed and being written to the memory card. For example, in his tests of the Nikon D200 in DPReview, Phil noted that the camera could take 22 shots before slowing down. How much bracketing do you do?   

http://www.dpreview.com/reviews/nikond200/page12.asp
[a href=\"index.php?act=findpost&pid=64476\"][{POST_SNAPBACK}][/a]

The D200 numbers are indeed impressive.

Even though my film camera supports up to ~15 auto bracketed frames with one click (two clicks per 36 exposure roll!), I have never used it. I typically spot meter in manual mode, and can't use auto bracketing since it is not supported. In fact after getting used to metering accurately this way, I now only bracket in really challenging situations.

[Jonathan Wienke]

A few thoughts on this thread:

If your camera has one, always use an RGB histogram when shooting ETTR, to avoid clipping individual channels. You will also need to set a manual white balance such that equal RAW values result in equal RGB values when your camera generates the internal JPEG conversion used to generate the histogram. With Canon DSLRs, the daylight WB preset is pretty close, other brands and models will likely vary. This is critical when shooting in situations with lighting that differs significantly from daylight. Gelled incandescent stage lighting will fool you into blowing the red channel severely if you use auto WB, and shooting before dawn and after sunset will often blow the blue channel.

The whole point of ETTR is to maximize the dynamic range of the scene that is captured by the sensor, which will result in the greatest S/N ratio in the captured image data. With a high-DR sensor and a low-DR subject, you have some fudge room to work with, but even in such cases, if you do not practice ETTR you are still compromising your image to some extent. Whether this compromise materially affects the final print will vary greatly from image to image depending on many factors, but I see no reason not to strive for the ideal exposure (non-specular highlights within 1/2 stop of clipping, but not clipped) that will allow the greatest flexibility in post-processing and printing.

We don't shoot JPEGs for most serious work, even though JPEGs are "good enough" in most cases; we shoot RAW to take advantage of the increased control and processing flexibility advantages the RAW format offers over JPEG. Few would argue that shooting RAW constitutes a license to "shoot sloppy" even though RAW files tend to be far more salvageable when Murphy's Law strikes. In the same way, properly applying ETTR gives one a margin of flexibility that may not be absolutely needed all the time, but sometimes can really save one's backside, especially when shooting difficult high-DR subjects. There are times one can get away with being sloppy and deviate from the ideal without negatively affecting the final print enough to be noticed, but that's no excuse to be deliberately sloppy about exposure, or any other part of our work.

Canon 1-series cameras can shoot at least 7 auto-bracketed frames 3 stops apart. Consult the manual regarding Personal Function 8 to set this up. I have my 1Ds and 1D-MkII set for 5-frame brackets when PFn 8 is on. For DR blending, 5 frames shot at 1-2 stop intervals is sufficient for just about any real-world subject.

[Ray]

...if you do not practice ETTR you are still compromising your image to some extent. Whether this compromise materially affects the final print will vary greatly from image to image depending on many factors, but I see no reason not to strive for the ideal exposure (non-specular highlights within 1/2 stop of clipping, but not clipped) that will allow the greatest flexibility in post-processing and printing.

[a href=\"index.php?act=findpost&pid=64686\"][{POST_SNAPBACK}][/a]

That's a very reasonable position to take, Jonathan   . My only reservation would be in situations where one is striving to capture the moment and one either has to make a rapid decision regarding exposure, or preset a combination of ISO, aperture and EC for use in evaluative metering mode, that one judges will cover most eventuallities for the conditions.

I would rather sacrifice ETTR considerations for the sake of getting the shot and I would rather expose one stop under the ETTR threshold than one stop over.

However, for me, the situation has now been complicated with ownership of a 5D. With the D60, a shot that was 2 stops underexposed at ISO 100 was hardly more noisy than an ETTR shot at ISO 400. I believe a similar situation applies to the Nikon D70 and D200.

However, with this extraordinary 'noise reduction' that's taking place at high ISOs with the 5D, it now really does seem to be sloppy not to strive for ETTR in every situation. I shall buy some 4gb, or even 8gb cards for my next trip and autobracket every situation where I don't have time to go through the spot metering routine, and those occasions are frequent. I just hope I don't get overwhelmed with images to sort through on my return.

[bjanes]

A few thoughts on this thread:

If your camera has one, always use an RGB histogram when shooting ETTR, to avoid clipping individual channels. You will also need to set a manual white balance such that equal RAW values result in equal RGB values when your camera generates the internal JPEG conversion used to generate the histogram. With Canon DSLRs, the daylight WB preset is pretty close, other brands and models will likely vary. This is critical when shooting in situations with lighting that differs significantly from daylight. Gelled incandescent stage lighting will fool you into blowing the red channel severely if you use auto WB, and shooting before dawn and after sunset will often blow the blue channel.


[{POST_SNAPBACK}][/a]

The idea of setting a white balance such that the camera histogram shows the raw channels with gamma correction and tone curve applied is a good one, but daylight balance will not accomplish the task for either the Canon EOS 1D Mark II nor the Nikon D200.

For daylight exposure of a white target such that the RGB values in an ACR conversion are equal and about 240 in sRGB, the Canon EOS 1D Mark II and the Nikon D200 produce similar values in the RAW channels. I have a CR2 file exposed in daylight and white balanced so that the RGB channels read 236 in the conversion. The RAW values as determined by DCRaw are 77, 148 and 115. For the D200 NEF the sRGB values are 241 and the RGB channels are 95, 178, and 136. The Canon allows a bit more head room, but the ratios of the channels are very similar. Both raw files have a decidedly green cast when viewed without white balance.

To white balance the above raw files, one multiplies the raw red value by 1.85 and the raw blue value by 1.26.

To have the channels of the converted RGB file equal to those of the raw file under the above conditions, one would have to apply a reverse white balance by multiplying the red channel by 1/1.85 and the blue channel by 1/1.26.

Julia Borg has published white balance coefficients for Nikon cameras showing similar with multipliers for the D200. Unfortunately, there is no color temperature having red and blue multipliers of 1.0 and 1.0.

[a href=\"http://www.pochtar.com/NikonWhiteBalanceCoeffs.htm]http://www.pochtar.com/NikonWhiteBalanceCoeffs.htm[/url]

Iliah Borg has devised a uniwhite balance that can be loaded into Nikon cameras so that the histograms represent the actual values in the raw channels after application of gamma correction and the tone curve.  Rather than using a color temperature, the white balance specifies the multiplers directly (red 0.55 and blue 0.74). I don't how this would be done for the Canon.

Shown below is the DCRaw conversion of the Canon raw file with no white balance. Since the file is linear (gamma 1.0), it appears dark.

[attachment=545:attachment]

[bjanes]

To have the channels of the converted RGB file equal to those of the raw file under the above conditions, one would have to apply a reverse white balance by multiplying the red channel by 1/1.85 and the blue channel by 1/1.26.

Julia Borg has published white balance coefficients for Nikon cameras showing similar with multipliers for the D200. Unfortunately, there is no color temperature having red and blue multipliers of 1.0 and 1.0.

http://www.pochtar.com/NikonWhiteBalanceCoeffs.htm

Iliah Borg has devised a uniwhite balance that can be loaded into Nikon cameras so that the histograms represent the actual values in the raw channels after application of gamma correction and the tone curve.  Rather than using a color temperature, the white balance specifies the multiplers directly (red 0.55 and blue 0.74). I don't how this would be done for the Canon.

[a href=\"index.php?act=findpost&pid=64746\"][{POST_SNAPBACK}][/a]

A note to clairify the uniwb of Mr. Borg. It sets the red and blue coefficients for white balance conversion to 1.0 and 1.0. The reverse WB is necessary only if one is going from an image that is already white balanced back to what it would have been in RAW.

To verify the behavior of uniwb, I took a photograph of a Macbeth color checker in daylight with the D200 with the uniwb as a preset for WB and opened the NEF in ACR. The preview with the as shot WB looked very green as expected. ACR reported the as shot WB as 5000 tint +10. To white balance, setting ACR to daylight did not work, and the picture still appeared quite green. White balance by clicking with the WB eyedropper of ACR on C4R2 was successful and the WB in ACR read 6750 tint +134. This was not the behavior that I expected.

In Nikon Capture, the uniwb shot showed normal WB when using the daylight setting rather than the as shot. Entering the multipliers manually as 1.82 and 1.38 for the red and blue channels also worked.

[Ray]

White balance by clicking with the WB eyedropper of ACR on C4R2 was successful and the WB in ACR read 6750 tint +134. This was not the behavior that I expected.

[a href=\"index.php?act=findpost&pid=64775\"][{POST_SNAPBACK}][/a]

bjanes,
It sounds to me that in the processing of reducing one problem (dynamic range) you are increasing another problem (accurate color). I don't think I would like to rely upon the eyedropper to get an accurate WB.

[bjanes]

bjanes,
It sounds to me that in the processing of reducing one problem (dynamic range) you are increasing another problem (accurate color). I don't think I would like to rely upon the eyedropper to get an accurate WB.
[a href=\"index.php?act=findpost&pid=64855\"][{POST_SNAPBACK}][/a]

Use of the eyedropper on a neutral target of relatively high luminance is the best WB. Alternatively, one can do a preset WB from a digital gray card. I don't think your intuition without any testing is a good basis on which to base conclusions.  

[Ray]

Use of the eyedropper on a neutral target of relatively high luminance is the best WB.

Maybe! But do all images contain such a neutral target of high luminance?

Alternatively, one can do a preset WB from a digital gray card

Doesn't doing that get you back to the initial position of compromising DR?

I don't think your intuition without any testing is a good basis on which to base conclusions.

I haven't arrived at any conclusions on this technique you've described. I'm just expressing an imression that the procedure sounds difficult, fiddly and time-consuming.

Could you post a couple of color corrected, WB corrected, sample real-world images demonstrating the increase in DR (or reduction in noise) that's possible with this technique?

[bjanes]

Maybe! But do all images contain such a neutral target of high luminance?
Doesn't doing that get you back to the initial position of compromising DR?
I haven't arrived at any conclusions on this technique you've described. I'm just expressing an imression that the procedure sounds difficult, fiddly and time-consuming.

Could you post a couple of color corrected, WB corrected, sample real-world images demonstrating the increase in DR (or reduction in noise) that's possible with this technique?
[a href=\"index.php?act=findpost&pid=64890\"][{POST_SNAPBACK}][/a]

Including a neutral target is a standard method for more advanced photographers. You don't have to include it in every picture, but only when shooting conditions change. You can't use uniwb (multipliers = 1) and the preset at the same time obviously, but you can store the preset for later use and use the uniwb for a better idea of the contents of the RGB channels on the histogram while you are shooting and then apply the proper WB in post. Since the WB is only a tag and does not affect the image data, it has no effect on dynamic range.

Balancing the channels can gain up to 3/4 stop in dynamic range and this has been demonstrated recently on the DPReview Nikon D2 forum with high resolution shots. It may not be worth the trouble in most instances, and I don't normally find need for it, but I was just following up on a suggestion by Jonathin and I think it is a very interesting concept. If you want to save time, use auto WB or just get a P&S.

[KSH]

To verify the behavior of uniwb, I took a photograph of a Macbeth color checker in daylight with the D200 with the uniwb as a preset for WB and opened the NEF in ACR. The preview with the as shot WB looked very green as expected. ACR reported the as shot WB as 5000 tint +10. To white balance, setting ACR to daylight did not work, and the picture still appeared quite green. White balance by clicking with the WB eyedropper of ACR on C4R2 was successful and the WB in ACR read 6750 tint +134. This was not the behavior that I expected.

In Nikon Capture, the uniwb shot showed normal WB when using the daylight setting rather than the as shot. Entering the multipliers manually as 1.82 and 1.38 for the red and blue channels also worked.
[a href=\"index.php?act=findpost&pid=64775\"][{POST_SNAPBACK}][/a]

Is the ACR behaviour due to the fact that "as shot" is not really as shot, but ACR's best guess as to what "as shot" really was, due to the infamous WB "encryption"?

Karsten

[bjanes]

Is the ACR behaviour due to the fact that "as shot" is not really as shot, but ACR's best guess as to what "as shot" really was, due to the infamous WB "encryption"?

Karsten
[a href=\"index.php?act=findpost&pid=65497\"][{POST_SNAPBACK}][/a]

No, the ACR rendering as shot is similar to the Nikon Capture as shot, so I conclude that ACR is reading the recorded white balance correctly. However, selection of daylight WB in ACR produces little change in the rendering, which is still far too green. In  Nikon Capture, the daylight setting produces the intended correct WB. When I set the WB with the ACR eyedropper, the resultant color temperature is 6750 +135

[bjanes]

Is the ACR behaviour due to the fact that "as shot" is not really as shot, but ACR's best guess as to what "as shot" really was, due to the infamous WB "encryption"?

Karsten
[{POST_SNAPBACK}][/a]

The answer to this ACR behavior was given by Thomas Knoll (ACR and Photoshop creator) on the Adobe Camera Raw forum:

[a href=\"http://www.adobeforums.com/cgi-bin/webx/.3bb6a85c.3bbfce73/2]http://www.adobeforums.com/cgi-bin/webx/.3bb6a85c.3bbfce73/2[/url]

The Nikon cameras have a doubble exposure feature, which sets the white balance coefficients to 1.0. With the white balance coefficients set to 1.0, ACR assumes that it is dealing with a double exposure situation and uses different processing.

[digitaldog]

Nothing wanting to go too OT, I was wondering if this new target would help in a number of ways:

http://www.babelcolor.com/main_level/White_Target.htm

I just got one and will play. But right off the bat, I could see it might be ideal for bracketing for deciding where the exposure for the best "expose to the right" values should be as well as for setting neutrals. Thoughts?

[bjanes]

Nothing wanting to go too OT, I was wondering if this new target would help in a number of ways:

http://www.babelcolor.com/main_level/White_Target.htm

I just got one and will play. But right off the bat, I could see it might be ideal for bracketing for deciding where the exposure for the best "expose to the right" values should be as well as for setting neutrals. Thoughts?
[{POST_SNAPBACK}][/a]

$69 for a little piece of plastic seems a bit high to me. The WhiBal for $29.99 seems like a better deal to me, but I haven't used either one of these devices. Thom Hogan (Nikon guru) does not recommend white for white balance and says gray works better, even though Nikon says white or gray works. I do not know what Canon suggests.

[a href=\"http://www.rawworkflow.com/products/whibal/index.html]http://www.rawworkflow.com/products/whibal/index.html[/url]

As for ETTR, why look for the small white spike in the histogram? --it wouldn't even be visible at a distance. As discussed previously, the histogram may indicate clipping when there is none and using it for exposure may result in underexposure. Why not just meter from a highlight?

[digitaldog]

$69 for a little piece of plastic seems a bit high to me. The WhiBal for $29.99 seems like a better deal to me, but I haven't used either one of these devices.

Well not all little pieces of plastic are created equally! The spectral qualities of this new target might well be worth the extra bucks. I can (and will) measure it with my Spectrophotometer. I don't have the $29.00 goodie so I can't compare it but with the $69 goodie, the spec's are impressive. Again, whatever the plastic is and how it reads spectrally is pretty important here. If not, we could use any little piece of white plastic.