DNG -> Camera Raw = dynamic range loss?

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DNG -> Camera Raw = dynamic range loss?

Postby Nathan » Mon May 30, 2011 11:38 am

Does the workflow for processing DNG files result in an unavoidable loss of dynamic range?

For example, when opening up a dng sequence into after effects, at first I am presented with the CameraRaw dialogue. Setting all sliders to their defaults, I had hoped that the raw floating point pixel data would come through to after effects. it would seem that I am mistaken.

In the below examples, I have brought in the dng sequence, ensuring all CameraRaw settings (except white balance) are set to leave the image in tact. Once inside after effects, I can see that the dng sequence is in "trillions of colors" and I have set my project up in 32-bit color.

But what I do notice is that the Dynamic range is compressed. By stopping down the exposure, you will notice that the highlights are clipping.

Image

But if I go back into the CameraRaw dialogue, and stop down the exposure by the same amount- it behaves as expected, I see that the floating point pixel values are behaving as expected and a nice superbright hotspot remains.

Image

Can anyone give me some ideas about how to preserve the dynamic range when working with dng sequences? or give me some further insight into what's going on?

Edit. Or is what i am seeing above, simply a difference in how the exposure treats gamma between the cameraraw dialogue and after effects itself- and in fact, the dynamic range itself is retained once inside after effects.
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Re: DNG -> Camera Raw = dynamic range loss?

Postby Biel Bestué » Mon May 30, 2011 11:46 pm

maybe After Effects is displaying the image within a specific color space like HD color space REC. 709? when you say 32bits you mean as a whole (8bit per chanel) or "per chanel"?
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Re: DNG -> Camera Raw = dynamic range loss?

Postby Nathan » Tue May 31, 2011 12:49 am

32 bits per channel.

I thought it might be a color profile issue,
But disabling color management completely still yields the same affect.

I sent the DNG over to a good friend who opened it in Nuke, and it behaved similarly, which makes me think that the way Adobe camera raw handles exposure is actually doing more than simply stopping down the luma- as you can see above, there is a rich orange cast coming through which makes me think there is some gamma adjustments occurring along with the luma shift.

I think all is good!
...i think... :)
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Re: DNG -> Camera Raw = dynamic range loss?

Postby Sebastian » Tue May 31, 2011 7:43 am

I just tried the same thing with 32bpc settings:
color_settings.jpg

color_settings2.jpg


And I can confirm that the filter changing exposure with the "Exposure Filter" and the "Exposure" setting in camera raw result in completely different images.

Some speculations:
-) It could be due to camera raw being able to perform different calculations that are only possible with the raw (bayer filter) data.

-) At Adobe the Exposure filter and camera raw code are being developed by 2 completely independent teams. Each of them applies their own developed math to the image. As you say maybe the camera raw team thought adding gamma changes when doing exposure changes actually works better but the exposure filter team did not make this conclusion yet....
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Re: DNG -> Camera Raw = dynamic range loss?

Postby carlos padial » Thu Feb 02, 2012 9:26 pm

it looks similar to this:

http://www.guillermoluijk.com/curious/h ... /index.htm
(see the second part of the article)

I also recomend many other articles inclosed in this blog.
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