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Beep6581 / RawTherapee

A powerful cross-platform raw photo processing program
https://rawtherapee.com
GNU General Public License v3.0
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Inaccurate Auto-Matched Tone Curve (Pixel 6a) #6674

Open dm30 opened 1 year ago

dm30 commented 1 year ago

Short description Hi. Unfortunately, when opening DNG on 'auto matched curve' profile, image appears too bright, colours perhaps inaccurate as well. Switching to neutral generates a muted output as expected. Interestingly, digiKam 'medium RAW preview' seems to take the exact values: its like taking the JPEG, then undoing all the processing* (exactly what I expect and often achieve with RawTherapee). See yourself below. By the way, I'll upload the original and other shots (in separate issue) just in case is mere lack of camera support. I really thank your work and support. I love this great software. Kind regards.

*JPEG shows greater dynamic range but this is due to the image-stacking -i.e. computational photography-, something not to be expected in RAW.

Steps to reproduce

  1. Take a picture.
  2. Open RawTherapee.

'Low ISO auto matched cuve' profile too bright with inaccurate colors.

Additional information

Other useful information:

imagen Here regular heavily processed JPEG imagen 'Medium RAW preview' as seen in DigiKam 7.9. In my view, preserving a very accurate representation of the scene. imagen

imagen Then RawTherapee's 'Auto marched low-ISO' curve profiled image and said curve ('similar to film' chosen) Finally, neutral profile for the sake of comparison. imagen

Lawrence37 commented 1 year ago

This is most likely because RawTherapee is trying to match the image with vignetting to the vignette-corrected JPG. Auto-match tone curve lifts the entire image in an attempt to match the vignette correction. The result is a center that is too bright and a peripheral that is still too dark. Unfortunately, the auto-matched tone curve doesn't change after enabling Flat-Field (your DNGs may have vignette correction parameters that the current dev can use through the Flat-Field tool). It seems logical to me that the tone curve should be calculated after the vignette correction is applied.

dm30 commented 1 year ago

Interesting. Makes a lot of sense. Is anything I can do to finding a solution?

Lawrence37 commented 1 year ago

There's not much you can do aside from diving into the code and coming up with a patch.

dm30 commented 1 year ago

By the way. I checked Lightroom. I at first did not notice its import is different as well. Looks good but colours are clearly saturated.
imagen imagen

Perhaps developers of 'libraw' (or whatever piece of software handles this in digiKam) may provide a hint. Isn't this library employed in Rawtherapee? Thank you.

kmilos commented 1 year ago

Re colors on Pixel DNGs, this is possibly related? https://github.com/darktable-org/darktable/issues/12515#issuecomment-1367472883

I think LibRaw does this multiplication internally (in contrast to dt's rawspeed), don't know about RT...