Re: Digital Negs - RGB vs CMYK

Michael Healy wrote:
>
> Kathrine, thanks for shedding some light on CMY. I know, on the surface my questions
> seem perhaps less than relevant.

Goodness, I certainly wasn't saying I thought your question was
irrelevant; I just said I wasn't sure I understood it. Thanks for
clarification. As to whether one uses black only or color inks when
printing inkjet negatives depends more on the printer than on anything
else, in my experience. I can't print the separations in color inks on
Pictorico with my ancient Epson Stylus EX, with any curve; I have to
print in black only on Pictorico. (And yes, I tried Dan's colorizing
methods but never got good results with them.) The black ink negatives
look like heck; it looks like it couldn't possibly print, it looks kind
of like a windowscreen, but for some reason it prints just fine. For
example this very delicate print was made from these window-screen black
ink negatives. In the original gum print, the tones and transitions are
totally creamy and smooth without a hint of graininess or a sign of the
grid-looking pattern that's in the negatives.

http://www.pacifier.com/~kthayer/html/skunk.html

I also have used paper color separations, (in fact 95% of the tricolors
I have ever done were done before inkjet printers got good enough to be
useful; most of my tricolors were printed from stochastic bitmaps
printed from 300 dpi or 600 dpi laser printers, thanks to Dan's book,
either on paper or on overhead transparency material). When I print the
inkjet separations on paper, then I can use all the colors. But the
color balance and the overall look is pretty much the same no matter
what negatives I've used: I print gum the way I want it to look, and the
negative is just the score as they say, it's not the music.... Which
is just another way of remarking how flexible gum is and what a wide
margin of error it has for color printing. For the record, it's my
considered opinion that at least 85-90% of the control for gum printing
is in the printing rather than in the negative itself, so in the end, as
I've said any number of times, I don't think the question of RGB vs CMYK
is a terribly important question.
Katharine Thayer

 The trouble is, while I'm not talking about colorizing,
> what I am talking about doing is allowing the inkjet printer to utilize all colors for b&w. I
> think it may have been Dan I got this from, in his book, that even when printing b&w, you
> may want to use color inks instead of "black only". The rationale is that you get better
> prints because as soon as it sees "black only", the printer, smart dude that it is, goes
> and drops your dpi by half or more.
>
> This past week, I sat down and experimented to see whether this is true of my Epson. It
> certainly was. My "all inks" neg - b&w - is vastly superior to the "black only" version. It's
> so bad that it's evident to the naked eye. Evidently Epson knows better than to waste dpi
> when all I'm asking for is the measly squirrelly old b&w imitation instead of the real thing.
> Since I'm enlarging 6x9cm's to 8x10", and only start out with a 2400 ppi scan, I sort of
> need as much dpi as I can get!
>
> So this is why I felt like I had to tackle this RGB-v-CMY controversy. Yes, these are b&w
> negs and separations, so it sounds weird to ask about it; but no, I am not printing with
> black only, I'm having to use all colors.
>
> Mike
>
> On 1 Dec 2004 at 12:56, Katharine Thayer wrote:
>
> Katharine Thayer wrote:
> >
>
> > > (3) GUM! If an inkjet printer does print CMYK, why do people use
> > > painter's (RGB) colors? It would seem to **require** that one use
> > > printer's (CMY) colors - assuming, at any rate, that one wants
> > > "realistic" colors. How come RGB pigments used on inkjet negs
> > > don't turn a gum print into something resembling cross-processed
> > > C41?
>
> I just re-read this and realized, I think, that I answered a different
> question than the one you were asking. I thought you were asking why
> some gum printers use color separations that they have generated by
> inverting the RGB file to CMY rather than converting to CMYK; that's
> the question I'm answering with my web page. But your question here
> seems to be about printing RGB colors vs CMYK colors on inkjet negs,
> which is a different question; as I say I'm not sure I even understand
> it. Color separations are in greyscale and are printed either in black
> ink or in colored inks to approximate black (at least I don't know of
> anyone who is making colorized color separations) the difference is
> whether the densitiesof the black on the CMY separations are
> determined by a straightforward conversion to CMY from the RGB file or
> whether the densities are generated by the default CMYK profile, which
> was designed to optimize the performance of a SWOP inks being printed
> from a high-speed web-offset printing press on clay-coated paper by
> altering the color values from true CMY to accommodate the
> requirements and limitations of these commercial printing machines,
> inks, and papers.
Received on Thu Dec 2 13:45:32 2004