Re: [Gimp-developer] darktable linear Rec709 doesn't match GIMP linear sRGB



On 04/27/2016 05:11 PM, Tobias Ellinghaus wrote:
Am Mittwoch, 27. April 2016, 10:55:14 schrieb Elle Stone:
The darktable plug-in linear Rec 709 chromaticities don't match the GIMP
built-in sRGB chromaticities.

Thanks for bringing that up, I changed the sRGB profile a while ago but somehow
forgot the others. I pushed a change to create profiles that match your sample
set. Could you please have a look at them [0]?

[0] https://houz.org/tmp/darktable_profiles_2.0.4.tgz


Using iccToXml to check the colorants and chad, the colorants and chad are perfect for all four profiles.

The darktable sRGB profile is a "V2 according to V4" profile with a point TRC. So this profile clips out of gamut channel values in floating point images.

GIMP's internal sRGB profile is a V4 profile with a parametric TRC, so GIMP's sRGB profile doesn't clip out of gamut channel values in floating point images.

I don't know what the actual rationale is for darktable to make a V2 version of sRGB. But at this point in time a V2 profile is the right choice for output to the web, for maximum compatibility with the various browsers (even Firefox doesn't read V4 profiles unless the user changes the gfx settings in about.config).

Best,
Elle



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