Problems measuring camera SNR with darktable and Raw Therapee

[heckflosse (Ingo Weyrich)]

@nathanm

Which are clearly due to bugs in RT.

That’s clear because the dev version - which apparently has a new approach versus the 5.8 release version - greatly improved the situation.

The old approach (automatic) is still needed for uniwb shooters.

@nathanm

I did not realize that I had resize enabled for RT. I will now rerun without it, but it would be very strange if that was the cause because the image was not actually resized.

I agree for this one as your pp3 resize setting was scale = 1

@nathanm

I had the camera / lens correction enabled and CA as a hold over from previous tests. But they are also enabled for most of the other raw converters I tried - including darktable, and CaptureOne. Not for dcraw, of course because it does not support that.

Raw ca correction in different raw converters work differently. Even raw ca correction in rt and darktable (though using the same base algorithm) work differently as rt by default does 2 iterations of raw ca correction.

On top of that, if I read your pp3 correctly, you used raw ca correction in combination with lcp ca correction. Use one or the other, but not both.