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

Re: separations for gum printing

" No need to even mark which is which, and --yes-- the differences are
also easily seen onscreen."

Boy, isn't THAT the case.  I used CMYK negs for many years before even
trying RGB and I never even had to label them. Looking at a set of RGB
negatives I still scratch my head wondering how they can contain all
of that different color data and look so similar.

On Thu, Nov 20, 2008 at 1:18 PM, Diana Bloomfield
<dhbloomfield@bellsouth.net> wrote:
> Hi Marek,
> With my admittedly limited experience with tri-color gums, my times are also
> fairly similar-- but I do think I also compensate with development time.  I
> did make a few CMYK prints, though (with the K printed as pt/pd), but those
> digital transparencies generated from CMYK (as opposed to CMY) are vastly
> different.  No need to even mark which is which, and --yes-- the differences
> are also easily seen onscreen.  Since I didn't print the black as gum, only
> as platinum, I didn't really get to appreciate what a CMYK would be like--
> all gum-printed.  Never used RGB, though.
> Diana
> On Nov 20, 2008, at 1:52 PM, Marek Matusz wrote:
> All,
> This recent discussion on tricolor gum printing sparked my interest. My
> printing times are about the same with all colors, but perhaps I compensate
> with development time, these two variables are related. But that is not what
> I wanted to discuss. Mostly everybody agrees that B channel (in the RGB
> color space) intended for yellow printing always requires a different curve
> then RG channels. This is also my observation and practice. The B channel is
> almost always much 'flatter" then oher channels and requires a more
> pronounced curvature. Quite frequently I do not have enough definition in
> the B channel to get enough contrast resulting in prints with overall yellow
> cast.
> 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.
> Marek
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