Blacks to specific cmyk values

davidrus · Posted: Mon Apr 14, 2008 6:44 am Post subject: Blacks to specific cmyk values

First, I apologize because I'm sure this topic has been covered, but I don't know what to search for so perhaps someone can shoot me a link to the correct topic if no one wants to answer.

I'm not really a beginner in photoshop, but this seems like a beginner question, so here it is:

I have line drawings in a layout that I scanned in. I'd like them to be the same or close to the black cmyk value of the text in the document. I'm not sure how to accomplish this. I tried channel adjustment and replace color, putting in the specific value I wanted (I read that c50 m40 y40 k100 was a good black for print), but nothing seems to work correctly. I would like to keep some kind of greyscale value (not make everything black), but I want the darkest shade to be that specific cmyk value. How do I do this? Thanks in advance.

combiBob · Posted: Mon Apr 14, 2008 2:32 pm Post subject:

OK, I'm not exactly sure what you're up to, but this is a quick way of changing CMYK black to a specific CMYK black. (Anything gray will also be solid with this).

Image>Adjustments>Curves

Add about 30-40% to your Shadow (Darkest areas) in all colors. Click OK.

Now all the colors in the lines should be 100%.

Go back to curves and pull the Cyan shadow to 50%, Magenta to 40%, Yellow to 40%, and leave the Black solid (100%).

davidrus · Posted: Tue Apr 15, 2008 2:31 pm Post subject:

I played around with your suggestion. It will definitely come in handy, but not exactly for this project. Let me try to explain better.

I scanned in a greyscale image. The blacks are registering at C75 M68 Y67 K90. So the darkest color is that value. I want to change that "black" value to something different and have the rest of the "greys" change accordingly. I'm thinking I have to do it Levels. If I could just tell it that the darkest color should be the value that I want, I'm guessing everything else would change relative to that value. I hope I'm explaining this correctly. I'm not much of a print guy, but I have this project I'm trying to complete. I don't even know if I have to do what I'm trying to do, or if it even makes sense, but if it is possible I'd like to know. Thanks again.

combiBob · Posted: Wed Apr 16, 2008 9:37 am Post subject:

Misunderstood "line drawings".

You could try Image>Adjustments>Selective Color>Blacks

IMO, the solid blacks are going to be too heavy, but...

Good luck to you,

bp

PS, I'm not sure I understand your original post. The part about CMYK black type? Normally, not a good idea for registration.

davidrus · Posted: Wed Apr 16, 2008 9:51 am Post subject:

Thanks again. I think I figured it out. I took the levels down in all channels with the channel mixer and then boosted them through curves. Worked perfectly, but alas, not going to do it anyway.

What do you mean about the CMYK black type? How should I do it? There's so much to learn about print it's a little overwhelming, but definitely interesting. Thanks again for your help.

davidrus · Posted: Wed Apr 16, 2008 9:58 am Post subject:

Nevermind. I get it. The plates may not be aligned properly. I guess text should be C0 M0 Y0 K100? So what if I want my black text to be a different color? Will there always be a chance of registration problems?

Matt · VIP

Hey davidrus,

I think you were right first time, a commercial black is sometimes referred to as 'rich' black and is made up of C=50%, M=50%, Y=50%, B=100%.

Hope this helps

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