Am Montag, 13. November 2017, 12:12:30 CET schrieb Manuel Coenen: > Hi, > > I have been using Color Balance a lot lately (mostly due to me not yet > having found out how to apply tone curves to only the red channel but > that's different topic) to remove light pollution from astrophotos. It > works great so far for me. > > When looking at the source code I see that it translates > > LAB -> XYZ -> sRGB -> apply changes -> sRGB -> XYZ -> LAB
Yes, that was maybe not the best design decision back then. > I am only post processing images for a couple of months and only lately > started to dive into the topic of color spaces. What I noticed is that > darktable (I don't know since when) also supports ProPhoto RGB color space. Well, darktable has always "supported" ProPhoto RGB as input/output space when providing it with an ICC profile. There is no built in version of that though, and editing isn't happening in fixed RGB spaces either. > And AFAIK this color space is much closer to LAB than sRGB. > > My question now is: would it be an improvement in terms of accuracy and > "available" colors to use ProPhoto RGB instead of sRGB as an intermediate > color space to apply the changes to? The color balance module doesn't clip colors, so the available colors are the same. The big problem with the current code is the gamma curve. IIRC I did that to mimic the behaviour in some other software, but I can't remember any details any more. Eventually we might move the module to some fixed RGB space part of our pipe, probably using linear Rec2020. > Best regards > Manuel Tobias
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