Unusual color and contrast difference when exporting and downsizing an ARW file to output 8 bit JPG from Lightbox

[KIRSJ]

Describe the bug

Go to 'additional context'... I am not able to provide files. I just want to describe the phenomenon based on more than one year of daily editing in Darktable without this problem - has this problem been reported by others. Normally using Darktable and lately version 4.9.0-549-g0fbd178e3 the Export function typically to 8 bit JPG at 80 percent quality creates JPG copies close to be visually identical to the source raw file (ARW). The latest image shows a discrepancy in color and contrast. The original and often slightly cropped raw file, i.e. almost original size, is exported with the following parameters: JPEG (8-bit), 80, auto, 2048x0, no, yes, sRGB (web-safe), relative colorimetric, none. Thumbnails use the raw file instead of the embedded JPG. This is my suspicion: With the actual image having a yellow-green foreground with grass isolated from the background of more grey-blueish tree trunks using a masking path in the Color equalizer module, it seems as if the separation is lost in the copy and the editing making the grass more warm with a saturation - bleeds to the background - making it more warm and less contrasty.

Steps to reproduce

See the description above.

Expected behavior

The JPG copy is normally largely identical viewed in Lighttable.

Logfile | Screenshot | Screencast

No response

Commit

The Export function in Lighttable.

Where did you obtain darktable from?

GitHub nightly

darktable version

4.9.0-549-g0fbd178e3 and 4.9.0+776~g6667649af8

What OS are you using?

Windows

What is the version of your OS?

Microsoft Windows 11 Pro, version 10.022631

Describe your system?

Dimensioned for image editing.

Are you using OpenCL GPU in darktable?

Yes

If yes, what is the GPU card and driver?

AMD Radeon RX 6600

Please provide additional context if applicable. You can attach files too, but might need to rename to .txt or .zip

The same behavior for the mentioned versions of Darktable. A TIFF file from editing the same ARW-file in Affinity exported to the actual Darktable folder - and stripped from the xmp-file - can be exported to an identical JPEG using the same settings in Darktable. Fresh edit: The problem seems to be introduced with the Haze removal module here used at 0.51 strength.

[KIRSJ]

I think the Haze removal module is not being written or read properly to/from the xmp-file.

[jenshannoschwalm]

Another round of "haze removal" issue so basically a duplicate.

[KIRSJ]

jenshannoschwalm, Duplicate of which report, could you be more specific?

[jenshannoschwalm]

@KIRSJ see above PR. If i misunderstood your issue please provide more precise information including at least the rawfile and xmp . Also i was not sure what you were comparing exactly.

[KIRSJ]

jenshannoschwalm, Thank you. The #17650 explanation goes over my head, as I am not directly involved with the Darktable code. My observation is a shift in contrast and colors using this module when the (ARW) raw-based output from Darkroom is exported to a JPEG. If the technical explanation in #17650 covers that then good, otherwise I can't provide further documentation. Sorry about that, but wanted to ring the bell anyway should others have had a similar problem. I rarely use the Dehaze removal module. But as far as I understand is has not been flagged as problematic when using the scene-referred (filmic) mode.

[jenshannoschwalm]

1. You might share the raw and xmp file with your edits so i could investigate if there are other problems :-)
2. It's not about scene-referred mode at all. Haze-removal had some code parts missing leading to a more stable/correct result. It will be much better after the mentioned PR has been merged.

Anyway, thanks for reporting and thus reminding me to fix this :-)

[KIRSJ]

jenshannoschwalm, Thanks for the clarification. When do you think the fix will be available from nightly builds?

[jenshannoschwalm]

Pretty soon i think :-)

[KIRSJ]

Good, thanks.