RE: RGB vs CMYK: gamut and some important notes for CMYK users

Thanks for the info.

Gerry G

-----Original Message-----
From: Keith Gerling [mailto:keith@gumphoto.com]
Sent: Saturday, December 11, 2004 9:27 AM
To: alt-photo-process-l@sask.usask.ca
Subject: RE: RGB vs CMYK: gamut and some important notes for CMYK users

Hi Gerry -

I hung those larger prints from brass grommets. I don't recommend it.
I needed a cheap method of hanging over a dozen very large prints.
Cheap it was. But some potential buyers expressed disapproval, and it
wasn't all that successful as the prints tended to sag in the middle.
Next time I'll attach the print to a support.

Keith

-----Original Message-----
From: Gerry Giliberti [mailto:GGiliberti@controlotron.com]
Sent: Tuesday, December 07, 2004 7:52 AM
To: alt-photo-process-l@sask.usask.ca
Subject: RE: RGB vs CMYK: gamut and some important notes for CMYK users

Keith,
What is that hanging method used in the link
http://www.gumphoto.com/cmyk.htm
How are the prints attached to the hanging wire?

Gerry G
-----Original Message-----
From: Keith Gerling [mailto:keith@gumphoto.com]
Sent: Tuesday, December 07, 2004 3:26 PM
To: alt-photo-process-l@sask.usask.ca
Subject: RE: RGB vs CMYK: gamut and some important notes for CMYK users

Judy asks:

Keith -- WHAT ARE YOU TALKING ABOUT?

<snip> and then "(Consider that an aside, not my question(s),
which are:)"

***When you speak of the Photoshop "inksets" then, you don't mean actual

physical sets of actual physical inks, but theoretical combinations of
(a)
monitor colors, and/or (b) printer ink colors that will be generated by
these specifications?

As a preface to answering this, I'd like to mention again that I use
both RGB and CMYK to make separation negs for gum printing. People have
asked me why. In a nutshell, RGB is much easier because there is less
control and less one has to understand. If it works with RGB, great!
No having to deal with all of these CMYK settings. But often I find
that I need more control (usually, because I just can't get dark enough
shadows using RGB).

Judy, when I say "inksets" I'm just using the word that the Photoshop
industry uses. The separation engine in Photoshop is calibrated to
address the needs of "ink users" as "gum users" are still a rather
insignificant segment of the Adobe user population. But if you hitch a
ride of the CMYK wagon, there is no way you can avoid ink settings
because that is what CMYK is all about. I have no experience whatsoever
with commercial inks, but apparently they are different. Change your ink
parameter in the drop-down ink selector of your CMYK settings, and you
have a different set of rules and therefore your separation negs will be
different. Different enough to matter? Well, that depends upon your
needs. Certainly it is different enough to notice:
http://www.gumphoto.com/cmyk.htm
Check out the way that those browns (designated by the blue dots) are
handled by the M and Y channels of the various inks. Pretty different -
and I'm not so sure I prefer the "default".

*** At the present time I have been making work prints (photos, not
negatives) on the 1160 -- using the settings in the 1160 printer
directory. I take it for those purposes there's no reason to dink around

with the Photoshop color settings.... or is there? If so, would 1160
care?

I have no idea. I don't know what an "1160 printer directory" is, and I
haven't used an inkjet printer in years. I'm not big on testing, but
I've always got the impression that you are. Why don't you test it?

"Again, Keith, you're way ahead of me, but for starters, I take it
you're
talking about "on the monitor" toggling. I won't torture you with more
questions (now), but can you make a general estimate of how closely
monitor image changes in such comparisons would (tend to) relate to
print
changes in negatives made from each set of settings?

Quite significant, as the above demonstration shows.

Personally, as a person who eyeballs all of my emulsion mixtures and who
doesn't own a scale, I don't pay that much attention to making sure the
color spaces are dead on the money. Heck, I don't even use a "gum
curve". But I thought it prudent to learn the rules before I broke
them. Some people here think that RGB separations make different prints
than CMYK separations. I don't prefer one over the other. I'm not
trying to say any method is better than another. My involvement in this
thread was purely a futile effort to try to correct what I feel are some
erroneous conceptions about the CMYK process.
Received on Mon Dec 13 09:35:12 2004