Help! Grayscale picture in CMYK Mode => not only K

Gerry Kunz wrote:

Hello,

I have a grayscale picture which I have top build in into a folder. The folder will be printed in a printing house via offset-print. In the folder there are color elements too (CMYK photos, etc.) and this greyscale picture. When I change the mode in Photoshop from grayscale to CMYK, I realized, that there are not only K values in the picture, but also CMY values. When I import the picture in my graphics software od print it out, I can see a slight color cast. What can I do with the picture to transform it into a picture which has only K values (CMY=0)? The picture should be printed in K process color only.

Thanks
Gerry.

On the layer(s) that you want grayscale go to Image>Adjustments>Channel Mixer and check Monochrome. Use the sliders (leave Constant at zero) to get the look you want. Other layers will not be affected.

You can do this with an Adjustment Layer as well. Group layer with Adjustment Layer to make sure layers below aren’t affected if necessary.

—
Comic book sketches and artwork:
http://www.sover.net/~hannigan/edjh.html
Comics art for sale:
http://www.sover.net/~hannigan/batsale.html

Gerry Kunz wrote:

I have a grayscale picture which I have top build in into a folder. The folder will be printed in a printing house via offset-print. In the folder there are color elements too (CMYK photos, etc.) and this greyscale picture. When I change the mode in Photoshop from grayscale to CMYK, I realized, that there are not only K values in the picture, but also CMY values. When I import the picture in my graphics software od print it out, I can see a slight color cast. What can I do with the picture to transform it into a picture which has only K values (CMY=0)? The picture should be printed in K process color only.

First select the entire picture and copy it. Then select the K channel only an paste the picture. Now your entire picture is in the K channel. Next, go to the other channels one by one, choose menu "Select all’ and hit delete.

—
Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.nl/

Johan W. Elzenga wrote:

Gerry Kunz wrote:

I have a grayscale picture which I have top build in into a folder. The folder will be printed in a printing house via offset-print. In the folder there are color elements too (CMYK photos, etc.) and this greyscale picture. When I change the mode in Photoshop from grayscale to CMYK, I realized, that there are not only K values in the picture, but also CMY values. When I import the picture in my graphics software od print it out, I can see a slight color cast. What can I do with the picture to transform it into a picture which has only K values (CMY=0)? The picture should be printed in K process color only.

First select the entire picture and copy it. Then select the K channel only an paste the picture. Now your entire picture is in the K channel. Next, go to the other channels one by one, choose menu "Select all’ and hit delete.

You can do that but I think you’ll lose a lot of the tonal quality that is provided by those other channels.

—
Comic book sketches and artwork:
http://www.sover.net/~hannigan/edjh.html
Comics art for sale:
http://www.sover.net/~hannigan/batsale.html

In article <43903b34$0$703$>,
"Gerry Kunz" wrote:

I have a grayscale picture which I have top build in into a folder. The folder will be printed in a printing house via offset-print. In the folder there are color elements too (CMYK photos, etc.) and this greyscale picture. When I change the mode in Photoshop from grayscale to CMYK, I realized, that there are not only K values in the picture, but also CMY values. When I import the picture in my graphics software od print it out, I can see a slight color cast. What can I do with the picture to transform it into a picture which has only K values (CMY=0)? The picture should be printed in K process color only.

You can use the Channel Mixer or Copy->Paste as others have suggested, but I’ve found the fastest way to force a CMYK grayscale image to the K channel only is to use the Hue and Saturation command. Turn on "colorize" and turn the saturation to 0.

—
Art, photography, shareware, polyamory, literature, kink: all at http://www.xeromag.com/franklin.html

"Gerry Kunz" wrote
….

Hello,

I have a grayscale picture which I have top build in into a folder. The folder will be printed in a printing house via offset-print. In the folder there are color elements too (CMYK photos, etc.) and this greyscale picture.
When I change the mode in Photoshop from grayscale to CMYK, I realized, that there are not only K values in the picture, but also CMY values. When I
import the picture in my graphics software od print it out, I can see a slight color cast. What can I do with the picture to transform it into a picture which has only K values (CMY=0)? The picture should be printed in K
process color only.

Reseparate your grayscale image specifying Max GCR, and the correct dot gain value for your press. This will give you a K only version of your image. Pasting the grayscale image directly into the K channel is almost certain to produce too dark a result because of the lack of dot gain compensation.

Tacit is correct that you will lose subtle gradations by printing only to the K channel. You can retain some of this gradation, while minimizing color casts, by separating with GCR set to heavy or medium. This puts more of the image into the K plate, and reduces the chance of any color cast in the final printing.

BTW – the color cast you see in your graphics software may not be significant. Illustrator and Quark, for example, use a quick and dirty preview method for placement purposes only. In certain versions of these programs, the CMYK looks bad on screen, and bears little relation to what is finally printed.

The best, and only, book that deals with these issues in a digital setting is Dan Margulis’s Professional Photoshop.
—

Mike Russell
www.curvemeister.com