Can of worms...
A second attempt at summary and proposed action:
1. D50 vs D65 doesn't make any difference as long as Lab values aren't
communicated to the outside. (E.g. by saving to a file or by having a
Lab color picker)
2. The 'natural' conversion for sRGB seems to be D65. So I'll use that.
[ Any plug-in that wants something different than D65 will just
have to do its own conversion for now. ]
3. To keep the door open for a later implementation of full color
profile support, I'll add a reserved parameter to all Lab functions that
either accept or return RGB values. (The layer modes could then still
choose not to use that and stick with default sRGB / D65)
Gimp-developer mailing list