On 12 August 2010 00:17, Edward Coffey <edward.cof...@gmail.com> wrote:
> My understanding of GEGL (and, I assume, a fully GEGL-based GIMP) is
> that colors will be represented internally as linear-light RGB(A)
> structures. Given that (and please correct me if I'm already veering
> off track), how are the red, green and blue illuminants defined? Are
> they "virtual colors" that lie far enough outside the visible gamut
> that they can completely contain it? Or are they something else, like
> standard sRGB illuminants, or illuminants related to the color-space
> defined for the image being edited?

As yahvuu says, they are the sRGB primaries.

You don't need to worry that the sRGB gamut is rather small since,
because GEGL is using float, it can represent values outside the gamut
as less than 0 or greater than 1.

I suppose it also means that GEGL will be D65 rather than D50, since
[1, 1, 1] (gegl white) will be D65 white.

Photoshop (I think) uses D50 because the print world has traditionally
used D50. This was because prints could be viewed in a variety of
lighting conditions from daylight (D65) to Tungsten (about D35). D50
is a convenient half-way point for trying to make something that'll
look OK in both.

Scientific colorimetry has always been D65. sRGB picked D65 as it's
much closer to the D90 or so of most CRT tubes. .

John
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