Unsatisfying default settings on DNG files from GCam / mobile phone

[Olivier Croquette]

I am experimenting with raw files from a mobile phone, specifically DNG files from the Google camera app on a Pixel 3a. Some files look OK in ART, but some others have very weird, fade colors. I have attached some samples, including screenshots.

I did some research and I found the following related discussions, but I don’t know if they are related to my issue:

https://github.com/darktable-org/darktable/issues/8728

https://discuss.pixls.us/t/dcp-camera-profile-from-smartphone-is-not-recognized-properly/24854

dcraw does not seem to be impacted though.

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[agriggio]

Hi,

I don’t think this is a problem of color profiles – if you use the embedded one the colors look like what you would expect to me.

The problem is probably due to the auto-matched curve that “fails”, in the sense that the tone curve that it computes doesn’t give the out-of-camera look.

Fixing this might not be possible though, as google phones apply a lot of tricks to produce their jpeg, which cannot be emulated using a simple tone curve.

That said, I found that usually just enabling haze removal and bumping the saturation a little bit gets you much closer to the camera look. Maybe you can try that?

[Olivier Croquette]

Thank you for the quick reply. Correcting manually like you described is feasible, it is what I did so far, but it is not practicable as a standard workflow. Feel free to close this report if you don’t think a solution is in sight though.

[agriggio]

one thing that you can try is to not use the auto-matched curve, and use the tone curve of the embedded profile.maybe that gets you closer – at least I would expect it should (I haven't tried though)

[Olivier Croquette]

Thanks, discarding the auto-matched curve really helps on some pictures. I am not sure what you mean with the “tone curve” of the embedded profile though. If you mean “Color” / “Color Management” / “Input profile”, switching between “Embedded” and “Camera standard” (the default) does not make a big difference, even though “Embedded” is a bit more blueish.

I also found out that the “Haze Removal” tool can help, especially with the shadows.

I have now an acceptable output for the sample picture I attached here earlier, which is not the case for another picture, which has a much higher contrast. Unfortunately, I can not share it, because it shows some persons.

By the way, it looks like some versions of GCam are able to merge different exposures in a single DNG file. I am not sure if this is the case here, and if could play a role.

Here are some related links:

https://forum.xda-developers.com/t/dcp-google-camera-dng-raw-calibration-profile.3881887/

https://www.dpreview.com/forums/thread/4538575

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[agriggio]

I mean this:

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[Olivier Croquette]

Great, that helps a lot too, thank you! The processed image of the RAW file I still had problems with now looks even better in ART than the JPEG from the camera. What is the easiest way to see the tone curve from the embedded profile? Maybe I can learn from it

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[agriggio]

closing as I don't have many ideas about what to change