Re: RGB vs CMYK: some experiments

Jim Morris wrote:
>
> This statement is true as the "default" CMYK set-up in Photoshop will
> attempt to gray balance the channels based on the spectral qualities of
> SWOP inks; but, for those so inclined, you can measure the L*a*b*
> coordinates of you gum pigments as they print on paper and replace the
> SWOP values with your pigment values in the custom ink set-up.
> Theoretically, Photoshop should attempt gray balance based specifically
> on your gum pigments (this, of course, assumes that you are trying to
> achieve realistic color using CMY pigments).
>

Hi Jim,
This sounds like a great solution for those who are having trouble
getting a good color balance in their gum prints, but it answers a
different question than the question I'm answering. I'm answering the
question "Is the default CMYK space the best way to get to quick and
straightforward CMY separations for gum printing?" This path is often
recommended by teachers; I'm just pointing out that the separations you
get by doing that are balanced for SWOP inks and so you might want to
think about whether that works for you or not, or whether a straight
inversion of RGB to the straight CMY values might be a better place to
start, which is what works for me. I stress again that I don't think
there is a right answer to this question, but I do think that people
should know what it is they are choosing.

The question you are answering is "How to get the best custom CMYK
separations for gum" which is a good question but a different question,
which I leave to those who are interested in it. Since I have always got
better color balance than I really wanted with the RGB separations and
have altered the colors by changing pigments, etc to make them less
realistic, I have no need to work for a better color balance, and will
leave that to others to work out.
Katharine Thayer
Received on Fri Dec 3 11:44:05 2004