On Nov 20, 2008, at 10:52 AM, Marek Matusz wrote:
> Mostly everybody agrees that B channel (in the RGB color space)
> intended for yellow printing always requires a different curve then
> RG channels. The B channel is almost always much 'flatter" then
> oher channels and requires a more pronounced curvature.
Point of clarification: Actually, unless I've been misreading these
discussions, this is opposite what other people are reporting, which
is that the separation for yellow requires *less* curvature than the
others, not more. For example Henry Rattle: "Yes, the Y curve is
quite a lot closer to the 45 degree line - less sigmoid" On the
other hand, I find no appreciable difference between the curves for
the three colors. To me, the fact that some say yellow requires less
curvature, some say it requires more curvature, and some (well, one
anyway) says the curves for the three are essentially the same
suggests that the crucial variable(s) influencing how the curve looks
must be something other than the hue range of the color.
I took screen shots of my curves for PV19, thalo, and PY97 (a
combination I've been using lately for tricolor test prints). The
curve for yellow is slightly more curved than the other two,
suggesting slight agreement with Marek that the yellow requires more
curvature, but not enough to make a never mind, certainly not enough
to say that the "yellow" curve is way different from the others. I
didn't note which of the screen shots was which with the magenta and
thalo, but they are so much alike it really doesn't matter.