Re: Digital Negs - RGB vs CMYK

From: Michael Healy ^lt;[email protected]>
Date: 12/01/04-04:40:27 PM Z
Message-id: <41ADE5EB.7387.3B2AA21@localhost>

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


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 Wed Dec 1 16:41:39 2004

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