Reader Question About PDF’s, CMYK and Printing


Posted on July 10th, by Andrew Kelsall in Color Theory. No Comments

Please Share:

I received another question in regards to printing this week, and I thought I’d share it with you all so everyone can benefit from it. As always, I have kept some information private:

PDF's, CMYK and Printing header image

The Printing Question:

I studied graphic design at the Art Institute of [private], the year before they opened a computer design department. I never completed my degree and I never went back to learn computer design.

I have been hunting and pecking around the web trying to understand how it all works, but it is so scary. Everything I read, including your Top 15 Printing Mistakes article make it seem as though it would be impossible to ever have a successful computer-to-print project. Especially RBG>CMYK. I know what each are, and I understand a printer using four plates for CMYK, but I don’t understand how it works with a computer. In some programs, converting to CMYK creates different layers, so that would represent plates in the printing process, but how does a printer get that information from a PDF file?

I have Photoshop CS2. In that, the image barely changes when I change it to CMYK, and I do not see other layers. Is this legitimate? I guess it all, like I said, just scares me. I would like to start dipping back into the design field, but I’m a tad ‘out of date’.

Sorry to hammer you with all of these questions, I just think your site looks as though it could help me a lot, there are just some things I need to understand before I go on.

Thank you for any help you might be able to give.

My Answers:

In regards to your question “how does a printer get that information from a PDF file?”. Well, when you send a PDF file to print and it’s saved as a PDF/X-1a file (I think these are supported in Adobe CS2), this creates the separations for you, although it’s wise to check the separate plate simulations/channels with Abobe Acrobat Pro before sending to print and requesting a proof. Exactly how this is achieved by the computer doesn’t really matter as long as it works.

• For more detail on this PDF format, check out this article over on Pre pressure: The PDF/X-1a file format.

When you mentioned “when I change it to CMYK, and I do not see other layers”, I assume that after converting your file to CMYK form RGB (or if you converted a layered CMYK Photoshop file to another CMYK profile) you have noticed that there are no layers. This is because Photoshop has to flatten the image/file in order to make the conversion possible. You should only convert to another profile after you have finished working in layers.

Additionally, if the colour profile you converted the file to has colours that are similarly-produced in the new colour profile, you may see little difference in the image appearance. Moreover, you may need a good monitor/display to see noticeable changes — and oftentimes, these changes are more prominent when the file is printed.

Thanks for your question!

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