Re: RGB vs CMYK: some experiments

Hi Jason,
Thanks for the great visual, which shows how the default CMYK alters the
CMY values from the true values.

If you had inverted the RGB channels, turning them into negatives for
CMY, and had an expert gum printer print them on gum, I would expect a
closer approximation to the original than you got by importing the
channels to CMYK, which of course altered the color values to match the
SWOP profile, which was my whole point, and thanks for the illustration.

It looks like the settings dialogue box has changed since my version of
Photoshop (I kept up from versions 1 through 5 and then stopped
upgrading) although I did check to make sure that the CMYK default
settings haven't changed in the newer versions (they haven't). It's too
bad that the new color settings dialogue just names the CMYK profile
rather than describing the settings. I go through all the settings on
the page that I would guess you didn't take the time to read, since your
page seems to show no knowledge of the information contained therein,
such as how an RGB file turns CMY when you invert it, and how the
default CMYK alters the true CMY values to match a profile that's not
terribly relevant to gum printing. I'll give it here again just in case,

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

Katharine Thayer

Jason DeFontes wrote:
>
> I've been trying to wrap my head around this since this thread started, and
> I finally decided to do some noodling around in Photoshop to see if I could
> understand it a little better. And I took some notes:
>
> http://www.toad.net/~jdefontes/rgb-cmyk/
>
> Hope it's helpful to someone.
>
> -Jason
>
> > -----Original Message-----
> > From: Katharine Thayer [mailto:kthayer@pacifier.com]
> >
> > I've been thinking about this whole question of why some people prefer
> > CMYK and others prefer RGB, and it seems to me that perhaps you could
> > make a case for the proposition that people who came to color gum
> > printing from color photography think in terms of color photography
> > when approaching gum printing, and the RGB route makes more
> > sense to us.
> > But for people coming from printmaking, or from commercial printing or
> > pre-press, then the CMYK route may seem more logical. Just a
> > thought....
Received on Fri Dec 3 10:39:22 2004