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Author Topic: Dynamic range - some examples  (Read 61548 times)

ErikKaffehr

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Dynamic range - some examples
« on: December 01, 2017, 09:26:50 am »

Hi,

There is a lot of talk about DR. Athough DR is an important parameter I often feel the need for DR is over emphasized.

Let's look at an image with high Luminance Range, shot with a camera with relatively small DR:



That image looks pretty good to me...

Now, take another image, shot with a camera that has a bit better DR:



It may be argued that either image may be better. But the DR advantage of the second camera is not that obvious. Now, let's look at some detail:



Here, the piano is quiet noisy. Now, let's look at the image with the camera having higher DR:


The second piano image is much cleaner. The first camera was 2007 generation CCD while the second one was 2012 generation CMOS. Modern CMOS sensors use thousands of analogue digital converters in parallell allowing for slow conversion times, while the older CCD designs used a handfull of off chip analogue to digital converters where each converter was very fast.

So, the reason modern cameras have higher DR is because they can reproduce darker areas with less noise.

There is nothing like highlight DR. Any sensor will clip at some well defined point. Expose beyond that and detail will be gone.

But, a sensor with clean readout can allow for some underexposure, that may be used to protect highlights.

Modern sensors can handle 13-14 EV of Engineering DR. But, monitors may handle just 9EV and prints even less. So, we need to map the high density range of the sensor to the narrow luminance range of the monitor or the reflectance range of the print.

Best regards
Erik
« Last Edit: December 01, 2017, 11:23:20 am by ErikKaffehr »
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Erik Kaffehr
 

DP

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Re: Dynamic range - some examples
« Reply #1 on: December 01, 2017, 10:03:24 am »

I think you post these very pictures of that concert hall on this very forum many times about this very topic...
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digitaldog

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Re: Dynamic range - some examples
« Reply #2 on: December 01, 2017, 10:20:16 am »

Athough DR is an important parameter I often feel the need for DR is over emphasized.
It isn't when the scene DR exceeds the camera's abilities to capture that range and the photographer wishes to capture the entire scene range.
Remember this example?
http://www.lumita.com/site_media/work/whitepapers/files/pscs3_rendering_image.pdf
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Andrew Rodney
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ErikKaffehr

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Re: Dynamic range - some examples
« Reply #3 on: December 01, 2017, 11:26:04 am »

Yes,

Because they are a good example of the topic. The subject has a luminance range about 15EV, lens flare take into account.

Best regards
Erik

I think you post these very pictures of that concert hall on this very forum many times about this very topic...
« Last Edit: December 01, 2017, 11:47:43 am by ErikKaffehr »
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Erik Kaffehr
 

ErikKaffehr

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Re: Dynamic range - some examples
« Reply #4 on: December 01, 2017, 11:34:51 am »

Hi Dog,

The luminance range indicated in the picture is 30000/60 -> 500 -> 9EV, that is easily handled by any modern sensor.

Best regards
Erik


It isn't when the scene DR exceeds the camera's abilities to capture that range and the photographer wishes to capture the entire scene range.
Remember this example?
http://www.lumita.com/site_media/work/whitepapers/files/pscs3_rendering_image.pdf
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Erik Kaffehr
 

digitaldog

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Re: Dynamic range - some examples
« Reply #5 on: December 01, 2017, 11:51:52 am »

The luminance range indicated in the picture is 30000/60 -> 500 -> 9EV, that is easily handled by any modern sensor.


Keep reading if you can, try NOT to ignore the text above the image (Range of visible luminance in cd/m^2):


Scene dynamic range is the key concept to understand. Scene dynamic range is simply the range of the brightness that is measured from the darkest element to the lightest. In the real world, this ratio can be very large. The specular highlight of a chrome car bumper under the noonday sun could emit a luminance of 50,000 cd/m2. A portion of the same car’s black tire deep in the shadow of its fender may only emit .5 cd/m2. This represents a scene dynamic range of 100,000:1

Again not, modern sensors are not there!
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Andrew Rodney
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ErikKaffehr

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Re: Dynamic range - some examples
« Reply #6 on: December 01, 2017, 12:08:39 pm »

Hi Dog,

Yes, I agree on that. I was merely commenting on the image you referred to. When discussing exposure it is quite normal to exclude specular highlights.

We can easily expand DR going into HDR. But, handling specular highlights in a single exposure is difficult with traditional photography, as exposing for specular highlights would lead to very little exposure on the rest of the subject, leading to lot of shot noise.

It would be possible to build a system that has some pixels assigned to highlights, Fujifilm had some cameras with such technology. There is also some suggestion that pixels may reset during exposure, keeping count of the number of resets.

Please note that I am not saying that DR is not important, just that it is not the most important factor in camera choice. For a long time, Canon cameras were weal performers in DR at base ISO, but a great number of great pictures were shot with Canons. The latest generation Canon cameras have new technology, much improving on DR.

Best regards
Erik



Keep reading if you can, try NOT to ignore the text above the image (Range of visible luminance in cd/m^2):


Scene dynamic range is the key concept to understand. Scene dynamic range is simply the range of the brightness that is measured from the darkest element to the lightest. In the real world, this ratio can be very large. The specular highlight of a chrome car bumper under the noonday sun could emit a luminance of 50,000 cd/m2. A portion of the same car’s black tire deep in the shadow of its fender may only emit .5 cd/m2. This represents a scene dynamic range of 100,000:1

Again not, modern sensors are not there!
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digitaldog

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Re: Dynamic range - some examples
« Reply #7 on: December 01, 2017, 12:14:43 pm »

Yes, I agree on that. I was merely commenting on the image you referred to.
Quite an old camera (article itself is 11 years old) and still not enough DR. Handling specular highlights isn't the only issue here. Again, what you can't capture, you can't render. It's quite easy to find scenes that exceed the DR of your examples. And no, we can't extend the DR using HRD for LOTS of captures! You know, stuff that moves.  :D
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Andrew Rodney
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ErikKaffehr

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Re: Dynamic range - some examples
« Reply #8 on: December 01, 2017, 03:41:43 pm »

Hi,

Some pretty serious guys, like Iliah Borg state that maximum luminance range, at the sensor, is around 11 stops. Why? Because of lens flare.

Subjects like mine, circumvent that a bit, in that the light sources are just a very small part of the image. So, there is not a lot of light entering the lens and causing flare.

Another situation, that can be quiet demanding, is when you have mosaic windows in dark places. Those pose a real challenge.

On the other hand, media straggles a bit with luminance range. Prints may have a density range like 7.5 stops. A calibrated monitor may probably not exceed a luminance range of 400:1. So, even if you have a great DR, you need to do some pretty hefty mapping to get it represented on available media.

I am all in favour of having high DR and I mostly shoot cameras with pretty high DR, like the Sony A7rII that is my most used camera.

The image below shows the highlights on a constructed scene with 14-15EV of DR, I would say they are quiet similar:


Pushing the shadows in Lightroom was not possible, as LR applies different bias to camera systems. But, pushing shadows equally in RawTherapee gave these results:


In the pushed shadows, the advantage of the late generation CMOS sensor is very obvious.


Best regards
Erik

Quite an old camera (article itself is 11 years old) and still not enough DR. Handling specular highlights isn't the only issue here. Again, what you can't capture, you can't render. It's quite easy to find scenes that exceed the DR of your examples. And no, we can't extend the DR using HRD for LOTS of captures! You know, stuff that moves.  :D
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