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

[Tobias Ellinghaus <houz gmx de>]

Am Mittwoch, 27. April 2016, 18:18:38 schrieb Elle Stone:
> 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.

Good, thanks for checking.

> 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.

Yes, what would you suggest? Using a different encoding for the TRC?

> 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.

So is darktable's internal sRGB profile (the one you can select in "input color 
profile"). We just export with a V2 to make it easy to actually look at the 
image. And I don't expect people to export float images in sRGB.

> 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).

That.

> Best,
> Elle

Tobias

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