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Let’s talk about CMYK, baby – part 1: line screen meltdowns

Now that I’ve covered a lot of 3D stuff, let’s talk about some printing stuff, for those who don’t know too much about print. My background is as a magazine art director, and I’ve dealt with some tricky CMYK scenarios through the years. Today was one of those.

This morning I was awoke at 5 a.m. by a call from a press check. It was from a rep who was concerned about some graphic lines occasionally thinning in a template graphic I was using. When you’re given a magazine template you’re invariably given these types of elements, so you don’t think much of them, especially something as simple as some grey lines. Well, it seems, these grey lines were “special” in the euphemistic sense of “not too bright.” Whoever made them had designed these very thin lines at exactly 45° and then screened them at 50% black:

When you have lines this thin, it’s also a bad idea to try and mix three colours. It’s just not going to line up on a web press that shifts more than you’d like it to. But the real problem here was the angle of the lines combined with screening. I’ll explain why.

For those of you who don’t know how press printing works, colour images are made up of halftoned plates (cyan, magenta, yellow, black) that mix thickness of dots in variation to create a full gamut of saturation and luminance:

Conventional haftoning is done with these angles (if they were all the same, you’d only see one colour): cyan 15°, magenta 75°, yellow 0°, black 45°. Notice the angle of black? It’s the exact same as the angle of the template graphic above. What happens when you have a thin line and halftoning is that when the plates are made for the press, the screen door effect of the halftone alters these lines, thinning and thickening them depending on the position of the screen. Watch what happens as the halftone screen moves over a 50% grey:

If the lines were 50% cyan, and drawn at 15°, we’d being seeing the same effect there. This moiré effect should show up in proofs but the publisher opted for inkjet Sherpa proofs, where line screen isn’t simulated. So keep this in mind when making your graphics. AND STOP WAKING ME UP.

More esoteric CMYK nuggets coming soon.

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