This is, most probably, a user-error, but I cannot figure out what I am doing wrong:
Over the last 6 to 8 weeks - before and after the upgrade from 3.8 to 4.0 - I have been finding many of my images throw a red warning, as soon as I open the image in darkroom, about white balance having been applied twice. The fix is, in every case, very simple: change the white balance settings from ‘user modified’ to ‘camera reference’.
What puzzles me about this is how the white balance setting ends up as ‘user modified’ when I was sure that it was set to ‘camera reference’ for all my images in the first place. And, indeed, some of the images now flagged as having a white balance problem did not previously have this problem, but have not been edited at all in the last 12 months (for some of them).
Where should I start looking for settings/options/actions that are causing the white balance to be changed to ‘user modified’ without my realising it?
This has been reported a few times and the cause is not known (since usually the R,G,B coefficients don’t actually change when you switch from user defined back to camera reference). Best guess is that perhaps darktable is trying to compare two floating point values, and these are only ever approximations so it thinks they’re different. I’m not sure whether this has actually been raised on github or not, but it’s been mentioned on the IRC developers channel a couple of times. For an easier fix, you can just click the reset button on the white balance module (if you have scene-referred workflow selected in preferences).
There was an issue raised in GitHub about it. I think the issue started with the move away from Adobe coefficients.
Regardless the fix is to do a reset of the module or what I did was to create a style that sets the white balance to camera reference. I used it in my entire database and use it if I import something old.
@LateJunction: it’s not a “user error”. You don’t do anything wrong. Its a known issue that can’t be fixed in darktable code. It’s a consequence, for only some cameras, of a needed move from Adobe coefficients as @g-man explains.
The only way to avoid that white balance warnings would be to revert back that move (but a needed move) so a dead-end to fix that.
Note that this will only affect old edits. I suggest you to read that issue: https://github.com/darktable-org/darktable/issues/12134
You will have all infos and a simple way to fix it once for all. Note that the warning in that case doesn’t affect your edit (mathematically a little but visually not really, coeffs changed are really tiny).