Hi,

this is just a rough sketch of a bug report, I will add pictures eventually, probably after LGM.

I don't know if you @hanatos remember that I reported a strange behavior with regard of color management years ago. I think I reported it on pixls.us. Basically all my photos that were produced with vkdt had a very slight green cast, the color cast was more visible in photos with lots of white-ish colors like winter landscapes, or lots of sky with clouds. Well and you could not reproduce the bug. Inside vkdt the photos looked ok, but the exported JPGs had a green cast.

I now found out the reason for this behavior: It was the way I calibrated my screen. I calibrated it like this: I have a Benq Photo screen with a rather large gamut, larger than AdobeRGB. I first calibrated it with the Benq hardware calibration tool on Windows, then I booted into Linux and only profiled it and used that second profile created with Displaycal for editing. With the Benq tool, I usually calibrated to 6500K and 120cd. The largest native color space of the screen can only be enabled during hardware calibration. However, during the profiling with Displaycal, the software showed that the screen had a green cast (the green bar was significantly longer than red and blue). The reason was visible after profiling: The largest native color space is larger than AdobeRGB especially in the green area.

A few weeks ago I was kind of too lazy to boot into Windows for the Benq tool and skipped hardware calibration, and only calibrated with Displaycal. This way I only have a color space that is like 98% AdobeRGB, and it is almost exactly overlapping with AdobeRGB. I adjusted the RGB-values of the screen with the OSD to 6500K and set brightness to 120cd, and then just profiled. And the result is: there is no more green cast in the JPGs produced by vkdt.

Note: RawTherapee and darktable did not have a problem with my "old" "hybrid" way of calibrating my screen.

I don't know the technical explanation for this behavior but probably you do.

I mean the actual problem is that the Benq tool does not really calibrate to 6500K, even if I set it to 6500K, I know that since a long time. Displaycal measures a different, more greenish white point after hardware calibration.

The second issue is that apparently vkdt cannot display JPGs with an embedded ICC-profile properly:

Most of the pics that are visible in the screen shot were produced with RawTherapee, and they carry the RT sRGB profile. The magenta thumb was produced by vkdt, however.