I’m very new to Darktable, so I apologize if I’m doing something wrong or the question doesn’t make sense. I have a Nikon D7500 camera. When I copy RAW files to my computer, they look fine in my standard image viewer gThumb, for example:
However, when I open the same image in Darktable for the first time (with no .xmp file), it looks very discolored, as someone has greatly reduced saturation:
I played with some various buttons and slides around and found that if I go to “base curve” and change “preserve colors” setting from “luminance” to “none”, colors become much closer to real:
By playing with different curves and settings I can eventually tweak the colors to my liking, but it takes time and it seems odd that gThumb automatically gives me the right colors. This happens for every single image.
Question 1: Is incorrect “base curve” setting indeed the culprit here? Does it make sense to have “none” as default setting instead of “luminance”? The base curve is automatically set to “D7500” based on EXIF data.
Question 2: Even when I change the “preserve colors” settings to “none”, the colors are still not quite right. If you look closer at the example above, you can see that the cow has a weird green-ish color in Darktable compared to much more realistic brown color in gThumb. Note how RGB histograms are very different in Darktable vs gThumb. What other settings should I tweak?
Question 3. Is it possible that the default base curve for D7500 is wrong? How do I check that? Would it make sense to go through about basecurves | darktable to calibrate a custom base curve?
Question 4. How do I configure Darktable to automatically apply the same settings that gthumb does? It would save me a lot of time on manually fixing incorrect colors.
Question 5. Could this be caused by wrong settings somewhere else (camera, monitor, OS etc)? Seems unlikely to me because gThumb gets the right colors.
Camera: Nikon D7500 (with latest firmware 1.10).
Software: Darktable 3.0.1 compiled from source code. I have “auto-apply per camera basecurve presets” set to “on” and it seems to work (auto-select “D7500” curve).
OS: Ubuntu Linux.
AFAIK gThumb uses libraw to process RAW images. Where does libraw get base curves and other settings?