RE: Converting a Layered RGB File to CMYK
RE: Converting a Layered RGB File to CMYK
- Subject: RE: Converting a Layered RGB File to CMYK
- From: "CS Carl Stawicki (4211)" <email@hidden>
- Date: Fri, 14 Mar 2003 10:46:16 -0500
Blending modes in CMYK may blend colors differently than in RGB. One example
I can give real quick is Screen. On a sample RGB image, make a new layer and
fill it with black. Change the layer's blending mode to Screen, and all the
black should disappear. Convert the file to your favorite CMYK without
flattening, and the black layer will appear like cloudy white; not totally
invisible anymore. The reason is, an RGB black of 0r 0g 0b is equal to 0L 0a
0b, which will disappear in Screen mode (like white disappears in Multiply
mode), but when you convert 0r 0g 0b to a CMYK that has a normal ink limit
(like 300%), you get a black that is lighter than 0L 0a 0b, so Screen will
blend the colors as if the black was really a dark gray (which it is). You
would have to rework the CMYK file to have the same effect as the original
RGB.
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From: Ted Ramsaur
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Sent: Friday, March 14, 2003 10:12 AM
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To: email@hidden
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Subject: Converting a Layered RGB File to CMYK
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Amongst the jumbled tidbits of color management information I've
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acquired over the last few years, I recall an admonition against
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converting a layered RGB to CMYK. Some workshop, seminar or publication
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insisted that an RGB file must be flattened to get the best possible
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conversion to CMYK. I was recently challenged on this by a client who
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was just as insistent that it would make no difference in the final
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CMYK file. Well, after a couple of days of research in all the usual
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places, I have failed to come up with a technical explanation to
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support my argument. Aside for the obvious, i.e. additional layers
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create more work for the CMM, can someone give me a good technical
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explanation as to why converting the layered file is a bad idea. Also,
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do you know of an exercise in Photoshop that would demonstrate the
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problem visually?
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Many thanks to all who contribute so much here.
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Ted Ramsaur
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WORKING PICTURES, INC.
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Nine McDaniel Avenue
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Greenville, SC 29601
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Voice 864-235-5014
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Fax 864-233-4629
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email@hidden
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http://www.workpix.com
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