Re: Digital Negs - RGB vs CMYK

From: Michael Healy ^lt;[email protected]>
Date: 12/03/04-10:08:42 AM Z
Message-id: <41B02D1A.26722.C98BB01@localhost>

Dan and Mark, thank you very much for posting your explanations. All of a sudden,
certain things make an awful more sense to me. So far, the most perplexing part about
all of this has been trying to figure out what's really going on inside the brain of that
printer thingy over there. Nearly as bad as working with Twain. Your insights were
exactly what I needed at this juncture.


On 1 Dec 2004 at 11:12, wrote:

>Mike asked:

>(1) what difference does any of this make, if the thing has to end up
>CMYK anyhow? Why does it matter what your Photoshop mode is (assuming
>it is color, not b&w)?

The Epson printer drivers assume you are printing an RGB file so the
driver is designed to make an intelligent conversion from your RGB
image to the CMYK inks (or with the photo printers, it's more like
CcMmYKk these days) that the printer uses.

There are 3rd party RIPs (Rastor Image Processors) that will let you
control the individual CMYK output. And Epson has just released their
own "Epson Stylus RIP Professional" that probably does something
similar. It's about $200. For most of us, this isn't something we need
to mess with for either making prints or negatives.

>(2) If it is true that both RGB and CMY get turned into CMY by my
>inkjet printer, then In terms of inkjet printing (NOT print shop
>printing!), what exactly is it that CMYK advocates are advocating,
>that I should take this extra step to convert it? And what is it that
>the RGB advocates are missing, that they think they actually are
>pulling off an RGB print through a CMYK printer?!

I don't know what advantage there is to printing a CMYK image to an
inkjet printer...but there might be some on this list who know.

Keep in mind that making Separation negs is a different beast
altogether. For that, you DO want to split your channels into CMYK (or
CMY). Then you use these separated channels to make monochromatic,
individual negs on your inkjet printer. I don't want to turn this into
a sales pitch but I have 20 pages in my book that talk about this very
issue. The mechanics are somewhat hard to condense down to a paragraph
or two. ;^) > >(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?

That's a good question for the gum printers on the list!

Hope this helps!


On 1 Dec 2004 at 3:53, wrote:


The primary reason to keep files in RGB when doing standard color
printing with inkjet printers is that if you send a CMYK file to an
Epson printer, the driver will first convert it to RGB, because that
is what the printer is expecting. Thus you lose some of the
integrity of the image file if you convert it to CMYK first because
the file goes through two conversions. Most inkjet printer color
workflows and calibrations are based on using RGB files.

Mark Nelson
Purchase the book @
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Received on Fri Dec 3 10:09:29 2004

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