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

Re: separations for gum printing

See the comparison here:

(Curved negatives from RGB and CMY K=0 separations.)


21 Kasım 2008, Cuma, 11:09 pm tarihinde, Loris Medici yazmış:
> 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?
> Regards,
> Loris.
> 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.