CMYK Color Separation for offset printing


Hello I would like to ask how to do CMYK color separation for offset printing? Is it the same for screen printing i.e. spot colors? What would be the optimal DPI, Frequency and angles?

My mom sent me a single layer file to do color separation for offset printing.

Do I use photoshop or illustrator? Or is it something that is set on the printer rather than using photoshop or illustrator?

It's for a 3(H) x 5(W) ticket btw.

Thank you.

8/12/2015 6:16:00 PM

  1. First, make sure that it will indeed be printed on an offset printer because there are many printers who will print on digital printers where the input is expected to be RGB.
  2. If it will be offset printed, you may be better off converting your file to CMYK and letting them prepare the color separation. I presume you have a calibrated monitor. When you convert from RGB to CMYK you can judge the quality of the colors on your calibrated monitor.
  3. If you can obtain from the printer a device profile, you can do soft proofing to make sure nothing important goes out of gamut. If that happens you can make the necessary adjustments to bring them into gamut.
  4. Offset printing uses LPI (Lines Per Inch), find out what LPI they use on the requested paper and set your DPI to double that number as a rough guide. If they will print 120LPI set your DPI on the image dimensions to 240 DPI.

Conversion from RGB to CMYK is a lossy process so do this conversion on a copy of the file, once converted it will stay in CMYK.

8/13/2015 6:45:00 PM