On 01/12/2016 01:26 AM, Sven Claussner wrote:
- What exactly means 'supporting gamma-encodings other than the sRGB
TRC' for intense GIMP users (artists and scientists)?


On the one hand, one goal for high bit depth GIMP is to make it easy for users to produce radiometrically correct editing results without having to know a lot (or anything) about color management, color science, and the mathematics of editing algorithms.

This important goal has been implemented pretty well (a handful of editing operations still use perceptually uniform RGB when they should use linearized RGB, and vice versa).

On the other hand, intense GIMP users - that is GIMP users who do have a working understanding of color management, color science, and the mathematics of editing algorithms - need control over their RGB working space primaries and TRC.

Control over the TRC:

The following bug report: https://bugzilla.gnome.org/show_bug.cgi?id=758001 provides a partial list of reasons why some users will want complete control over the TRC that's used to encode their RGB data. This bug report requests a GIMP GUI option to completely disable the babl code that linearizes the sRGB TRC.

A user option to disable the babl flips would go a long way towards making GIMP 2.10/3.0 much more friendly to intense users, and could probably be implemented more easily than providing full support for arbitrary user-chosen TRCs.

Control over the RGB primaries:

sRGB has a very small color gamut. Full support for arbitrary user-chosen RGB working spaces for babl/GEGL/GIMP might not happen very quickly, rather might take several years.

In the meantime, having at least one hard-coded wider gamut RGB working space made available through the GIMP UI would go a long way towards making GIMP 2.10/3.0 more friendly to intense users. Rec.2020 or ACEScg would both be excellent choices. Both of these color spaces are widely used by people working with VFX/CGI/Film, and both seem to produce better editing results than the print-based/Adobe-centric ProPhotoRGB:

http://colour-science.org/posts/about-rgb-colourspace-models-performance/
https://www.freelists.org/post/argyllcms/White-Point,45.

I would recommend Rec.2020 over ACEScg because ACEScg uses an imaginary primary.

Hard-coded RGB working spaces for GIMP would be nice to have:

Even if high bit depth GIMP already provided support for arbitrary user-chosen RGB working spaces, a selection of hard-coded built-in RGB working spaces is a solution to a problem that I believe Pippin mentioned awhile back: There are an awful lot of poorly-made RGB working space ICC profiles floating around out there. Providing users with a small selection of well-chosen and properly made built-in RGB working spaces seems to me to be a good thing to do. So providing at least one wider gamut RGB working space for GIMP 2.10/3.0 wouldn't be wasted coding effort.

Elle
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