Re: Digital Negs - RGB vs CMYK

From: Dave Soemarko ^lt;[email protected]>
Date: 12/02/04-09:07:20 PM Z
Message-id: <000701c4d8e5$34759cd0$9729fea9@wds>

It is all just terminologies and it can be sometimes confusing. With CMY, C
prints C, M prints M, and Y prints Y.

With RGB, it is the inverse because what they mean is using the negative of
R, negative of G, and negative of B, which is C, M, and Y, respectively.

Some other confusions too, you might come across some old books where the
author uses red to mean magenta and blue to mean cyan. Usually these come
from non-printer type artists but not always the case. They usually picked
red color that was actually closer to magenta and blue that was closer to
cyan.

And if you are reading painting books, most of the time they don't talk
about CMY. The painters call our cyan blue or sky blue, our magenta purple,
our blue violet, our red orange, etc.

Dave S

----- Original Message -----
From: "Christina Z. Anderson" <zphoto@bellsouth.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Thursday, December 02, 2004 6:37 PM
Subject: Re: Digital Negs - RGB vs CMYK

> Whoops, I did not make my post clear; I have no problem or question with
the
> not using the K layer. That makes sense. My question is this:
> with CMYK does the C print cyan, the M print magenta, and the Y print
> yellow, as Livick says, or does the C print red, the M print green, the Y
> print blue??? And if C prints C and M M and Y Y, why is that not the case
> with RGB, too? Mind you, I've never done CMYK seps or felt the need to,
> having come to gum before digineg seps were possible and the option was
> color seps in the darkroom with RGB filters...
> Chris
> ----- Original Message -----
> From: "Kate M" <kateb@paradise.net.nz>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Thursday, December 02, 2004 12:23 PM
> Subject: RE: Digital Negs - RGB vs CMYK
>
>
> > Hi chris, I'm pretty sure he does exactly what he says - prints just the
> > CMY without the K, I was introduced to negs this way by John Pollard in
> > Australia. I've not found it to work for me. I think if you did one
> > printing for highlights, midtones and shadows, as the trad gummists did,
> > you would get away with this, as you'd be able to deposit more pigment
> > in the shadows. I've tried this, and it works, but it's very cumbersome
> > I think.
> > Kate
> >
> > -----Original Message-----
> > From: Christina Z. Anderson [mailto:zphoto@bellsouth.net]
> > Sent: Friday, 3 December 2004 2:22 a.m.
> > To: alt-photo-process-l@sask.usask.ca
> > Subject: Re: Digital Negs - RGB vs CMYK
> >
> >
> > Good morning all,
> > Whether anyone does or doesn't print exact color is not as interesting
> > to me
> > as the fact that you can print exact color in this age, without a lot of
> >
> > muss and fuss. I find that fascinating. I just betcha if diginegs were
> > available back in 1839 Kodak would be doing gum today :) Katharine,
> > interesting you should bring up Livick, as I've just reread his
> > book for the umpteenth time.
> > First I will say it is commendable he has shared his process step by
> > step,
> > and he is a master gum printer. Certainly I have to say his gums are
> > very
> > true to color.
> > He's certainly very anti-mixing your own gum from scratch, which I find
> > odd,
> > but I suppose he gets more predictability with using the same gum from
> > the
> > same manufacturer (if that is ever possible to have the same gum). I
> > started mixing my own from powder when I found out the Photographer's
> > Formulary did just that. I figured my food processor would work as well
> > as
> > their mixer.
> > Livick sprays his gum layers with a spray gun so probably he needs to
> > have a
> > very particular baume to never clog the sprayer, but for the rest of us
> > who
> > brush on, powder is great. I watched Sam Wang mix his gum/pigment
> > solution
> > **at time of use** with powdered gum (dump in powdered gum, water,
> > pigment,
> > dichromate), which dispelled any myth about not using powdered gum
> > immediately.
> > Anyway, this is not on the subject heading topic, so back to my Livick
> > question.
> > He uses CMY separation negatives, but also talks of RGB sep negs in
> > continuous tone..
> > On p. 53 he says he prints the yellow gum layer with the yellow neg, the
> >
> > magenta with the magenta, and the blue with the cyan. He does not use
> > the K. Not having ever done CMYK, is this a typo, or those of you who do
> > use CMYK
> > do you use the negs like this? Or is it just that the service bureau he
> >
> > uses labels the negs this way? In other words, RGB negs use the R for
> > cyan,
> > the G for magenta, and the B for yellow.
> > Chris
> > ----- Original Message -----
> > From: "Katharine Thayer" <kthayer@pacifier.com>
> > To: <alt-photo-process-l@sask.usask.ca>
> > Sent: Wednesday, December 01, 2004 4:04 PM
> > Subject: Re: Digital Negs - RGB vs CMYK
> >
> >
> >> Judy Seigel wrote:
> >>>
> >>
> >>>
> >>> On the 3rd hand, this is all probably overkill -- does anyone print
> >>> gum for exact "photographic" color repro?
> >>
> >> Stephen Livick does....
> >>
> >
> >
> >
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>
>
>
>
Received on Thu Dec 2 21:07:38 2004

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