U of S | Mailing List Archive | alt-photo-process-l | Re: separations for gum printing

Re: separations for gum printing

Hi Marek,

I first planned to start to make color gums by CMYK separations -> because
it seemed natural in context of "printing" + because it was the method
used by Keith. (I had not done anything serious with gum other than few
step tablet tests before participating his workshop...) Anyway, I dropped
the idea and started with RGB separations because it required only three
negatives, in other words less costly (1. both negative cost + less
layers) (2. yes K=0 also requires three negatives, but I wasn't
considering this at that time, and probably would not in the future, if I
wasn't reading your message).

I have an image which is currently giving me a hard time; I get perfect
highlights and midtones but muddy / lifeless / flat shadows. I tried to do
CMY K=0 separations and when I inspect the negatives on screen I see that
it would print even worse, because there's no useful detail in the
shadows. The RGB separations show good texture in the shadows, compared to
the CMY separations. How come?


P.S. I'm at my mother's house now, will post the comparison images later
and ask for your comments.

20 Kasım 2008, Perşembe, 8:52 pm tarihinde, Marek Matusz yazmış:
> ...
> Since CMYK space and separations are intended for printmaking, which is
> what we do in gum I started making CMY separations with K set to zero.
> There is a visual difference on how the pictures look on screen in these
> two color spaces (anyone interested should try to toggle between spaces in
> Photosop) and also how the Y separation looks compared to B channnel in
> RGB color space. It also seems like the colors are less muddy. I have only
> done a few pictures so far, but I want to see if anybody is doing
> different methods of generating separations for tricolor gums.