Re: CMYK separations on Adobe Photoshop

From: Joe Smigiel ^lt;[email protected]>
Date: 10/29/04-08:22:56 AM Z
Message-id: <s1821a1b.022@gwmail.kvcc.edu>

I forgot to mention a fairly obvious thing: once you have the channel
saved as a positive grayscale file you have to invert the positive to a
negative. This can be done under Image--> Adjustments-->Invert or by
having the printer set to invert the files during printing. I also flip
the image horizontally when printing so that the ink surface is next to
the emulsion of the paper.

By sheer coincidence, yesterday and today I have been testing separation
negatives made for gum printing on a new Epson 2200 printer using both
the CMYK mode and the RGB method I described earlier. I'll scan the
prints as soon as they dry today and put them online. Once on the web,
I'll post the URL in case you wish to see a visual comparison of the
results of both methods.

Joe

>>> jsmigiel@kvcc.edu 10/29/04 8:56 AM >>>
>>> mgalanmolina@hotmail.com 10/29/04 5:57 AM >>>
Hi list, there is a easy way, or not easy, to make cmyk separations on
photoshop other than change image mode to cmyk. I want to obtain the
separation channels as layers in order to apply curves over every layer
independently and save it as different files.

Thanks

Manuel, from Spain

Wih an RGB file (e.g., image.psd), open the channels window and select a
channel. For example, select the red channel. Then change the mode to
grayscale and discard the other channels. At this point, ***be sure to
rename the file*** (e.g., image_RED.psd). You now have a grayscale
positive of the Red channel and you have the original file still intact.
 Do the same with the other channels (G+B). Then, using the original
file, change the mode to grayscale (or desaturate the RGB file) and
rename it for the black channel.

Be aware that this set of negatives will be distorted in terms of color
printing characteristics compared to those made using the CMYK mode and
selecting those individual channels for negatives. The info preserved
just isn't the same, but can be interesting nontheless.

Also, why not use the channel mixer (Image-->Adjustments-->Channel Mixer
IIRC) to get the effects you desire in RGB and then switch to CMYK and
print out the separations?

Joe
Received on Fri Oct 29 08:21:42 2004

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