I noticed that when using the color calibration module that when setting the temperature in the module to the exact same value as the default and changing nothing else, a color shift occurs which can be seen in both the histograms and in an observable green cast in the image. I saw that there has been another post about a green cast with the color calibration module, but it appears to be a different issue.
This seems like undesired behaviour, but perhaps I am not understanding something about how the module works? I am happy to provide example images and/or screen shots if this is not able to be reproduced easily.
I am running the most recently released version of Darktable (3.4.1) on Arch Linux.
At least, make sure that in the normal white balance module the balance is set to “camera reference”, then do your white balance / color balance from the color calibration module.
From what I’ve understood, there were some bugs with d65/d50 differences in the color calibration tool which have been fixed in development version towards 3.6. But I don’t know when and how these might show up.
The K values in color calibration don’t really mean anything…so if you set it to 5000 K or some other desired WB you might introduce an unexpected cast. I am not the one to explain this properly but this is not a traditional WB linked to K values. I will see if I can find you the reference…If the initial default calcultated by CC is not what you want use the picker on a neutral element or change the selection to custom for the illuminant and you will get a hue chroma slider pair. Usually just tweaking the chroma of the calculated hue will dial in your WB.
In the settings I have selected the modern colour and scene referred workflow. If I double check that I am starting from a fresh history for an image that it still occurs. I can also confirm that the white balance module is set to camera reference. I observe this in every single image I process.
I understand that the numbers don’t really have a clear meaning, but the point here is that typing in exactly the same number that is apparently the default value that was either calculated or obtained from the metadata for an image does not result in the image staying the same, but instead introduces a cast. Note that this default value is different for each image. This means that if I am nearly happy with the default but want to every so slightly change the slider one or the other direction, it is not possible.
To be totally clear, I am talking about the default temperature in the color calibration module; I am not at all looking at the white balance module, I am just leaving it on the default camera reference. The color calibration module is active and I can type in the temperature it says it is using and the image changes, and when I click to restore to default it changes back. This appears to be different from the linked thread, where the comparison is being made to the temperature from the white balance module.
The color calibration has more settings than just temperature.
By default it appears as ‘pick from camera’ or something. When you ‘reset it’, it might not reset to that starting point, but to an empty point.
There is a key to hold to ‘reset to auto defaults’ which is different from ‘reset to defaults’… holding the ctrl key on windows at least.
Also, if you want to go back to how your camera took the shot, you can ‘reset to auto defaults’ but you can also pick the ‘as shot in camera’ option from the illuminant menu:
If the ‘adaptation’ is set to ‘none’, you first have to pick something, and then pick ‘as shot in camera’ again.
I do understand that there are more settings than temperature. But I think you have found the root of the issue: the default setting for illuminant is “as shot in camera”, but if you select that and then hit “reset to auto defaults” it changes the illuminant displayed in the GUI back to daylight, even though it is actually not using that. I do think this is misleading behaviour, as it implies that the default setting is the daylight illuminant with the temperature it has calculated and set in the slider.
Thanks for your responses; I was feeling not confidant about using the module because I thought I had found a bug.
