Newbie question about black point for offset printing

[Djuna_A_]

I am preparing files for offset printing.  I have the printing profile as "Japan Color 2001 Coated."

I do not have a monitor calibrator; I just want to optimize the blacks. 

When I go to Color Picker and select the CMYK values for "true black" (75/68/67/90), nothing seems to happen on my file. I also don't see the "step" when I go to the edit menu, so I'm confused.

Is there a way to simply apply "true black" universally to my 17 files? Is that even desirable, e.g. won't I run the risk of converting some desired greys to undesired black if I do this?  I don't have much visible black in my files, eg. there is no text, just a lot of color.

Any input welcome. Simple language, please; I'm not going to learn color management in depth... I just want to do the best I can for this project.

[Djuna_A_]

OH, I see now when I open each file, the CMYK values are the same. Does this mean they are APPLIED to each file automatically, ,i.e. whatever appears in the Color Picker viewer is applied?

[Derek Cross]

Best to leave your images in RGB color mode.

[Djuna_A_]

I would love to, but the profile is CMYK.

[Djuna_A_]

That is, the publisher has stipulated this profile. It's for an offset press.

[D Fosse]

The values you read out in the CMYK file are the values that get sent to press - the percentages of cyan, magenta, yellow and black ink. It's not more complicated than that.

For this to yield the correct colors in print, the file has to be made with the appropriate CMYK profile! Image > Mode > CMYK is not good enough. You have to ask the printer about this. If this goes over your head, you should probably follow Dereks advice and stick to RGB.

Text and graphic elements are usually printed on the black plate only, and this will overprint the other inks if set up to do so in the file.

Maximum black ink in offset print is not a particularly deep black. Check for yourself with various printed material. If you haven't calibrated your monitor so that monitor black matches this, you're in for a massive disappointment. This has nothing at all to do with the values in the file, only how it's reproduced on paper vs. on screen.

[Djuna_A_]

Thanks, D. Fosse. I do already know the profile. I don't know what plate they will be using, and I don't have a monitor calibrator. But you gave me the link to some, and I'll check it out now, as I got an extension on deadline. I think this issue will remain "over my head," or at least beyond it, until I actually see it in front of my head.

[Djuna_A_]

A lingering question as I wait for my calibrator to arrive: I get the calibrating to ambient light and color profile, etc. I know the paper is "coated." What I don't yet understand is if I can't know the paper color (the publisher doesn't know), and I'm wondering if there is a big difference between calibrating to printing on cream paper vs white-white paper...

Maybe this will become apparent as I work with the calibrator, but more thoughts welcome.