Grayscale to CMYK

KC
Posted By
Karl_Cartwright
Nov 26, 2003
Views
1184
Replies
5
Status
Closed
Photoshop 7 (Illustrstor 10) Windows 2000

What I want to do: Convert greayscale images to CMYK with the image only on the Black channel.

The problem: When converting a grayscale photo to CMYK in Photoshop, the image is spread across all 4 channels.

Partial solution: Create a custom color setting using Maximum black generation

The confusing part: Illustrator 10 will convert to CMYK without splitting the image across all channels (Using the Adjust Color filter), it stays in just the black – Using the same color settings as Photoshop.

I would like to better understand what is going on here. Can anyone give me some insight? Why does Illustrator do it one way and Photoshop does it another. And, since I live in my own little world of needs, Why would you want a grayscale image distribited on all channels? Just the rich black thing?

thanks
-kaz
Related Tags
cmyk grayscale

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RL
Robert_Levine
Nov 26, 2003
What are you trying to accomplish? There’s no difference between grayscale and a CMYK image if the CMY plates are empty.

Bob
KC
Karl_Cartwright
Nov 26, 2003
I have to add 20% yellow to the yellow plate. Which I can do.
L
LenHewitt
Nov 26, 2003
You will need to create a custom CMYK profile and set Black generation to Maximum
JS
John_Slate
Nov 26, 2003
….or copy the grayscale, choose file>new document and in the new doc dialog change the file type from grayscale to CMYK, then when the blank file opens up, target the black channel in the channels palette and paste.
GH
Gernot_Hoffmann
Nov 26, 2003
Karl,

I don´t understand your last message – didn´t you want to print by K-only ?

Coming from RGB, a Grayscale image is an RGB image with equal values R=G=B, using a predefined transformation (in PhS), which is IMO not related to any printing process.

The Grayscale to CMYK conversion depends on the selected CMYK profile. As a standard in PhS, this is always Rich Black CMYK (but why ?). The K-plate contains just the part K which is added by UCR or GCR.

One solution is, as you say, Maximum Black Generation (somewhat hidden). The other is:
Create a spot color channel in Black and copy the Rich Black CMYK image into this channel. The result is just this one channel which can have any name. Can we RENAME this channel for convenience to "Black" if the previous CMYK channels are deleted ? I hope so.

The reason for Rich Black: looks better. Can be done if the brochure is anyway printed by CMYK because of colors in other images.

Best regards –Gernot Hoffmann

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