I've become a great fan of Dan Margulis and his books on color
correction. See Photoshop Professional and Photoshop Lab Color. (BTW,
while the books are aimed at PS users, I've found them very good for a
basic understanding.) Almost all of his ideas can be implemented in the
Gimp, except for his use of the luminosity blending mode in layers.
Value blending mode is related, but it really doesn't work as well the
luminosity mode does in PS.
I can see Gimp calculates luminosity, but I don't know if this is the
same "luminosity" PS calculates, or, for that matter, how it's actually
used as a "blending mode".
In any event, I'd like to put it on the wish list for 3.0 (dare I hope
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