How to Decide: 4 Color or Spot Color?
May 14, 2013 by Nani Paape
In four-color process printing, all colors are printed in dots, in the four process-color inks. The four process colors are cyan (C), yellow (Y), magenta (M), and key (black). Yes, the "K" in CMYK stands for key . . . because in four-color printing the cyan, magenta, and yellow printing plates are keyed (aligned) with the key of the black key plate.
In traditional offset printing, those dots of color then form rosettes, like the ones shown [right]. Each color of dots is printed at a different screen angle.
The easiest way to understand four-color process is by looking at the cartoons in the Sunday paper. The dot pattern is printed so coarsely on the newsprint that you can see all the dots.
Notice how your eye interprets the dots as continuous colors. It’s like magic. If you have a magnifier or loupe, you can look at any printed page to see whether it’s printed in dots or solid inks.
Digital printing does not always create a rosette pattern. Some digital presses create a dithered (scattered or sprayed dot) pattern that looks more random, similar to inkjet printing.
Four-color process printing is necessary if your design includes full-color photographs.
Areas of color that look like a solid, single color can be created from CMYK dots. These are called four-color builds. Some greens, browns, oranges, and pastels are hard to reproduce as builds.
On a digital or offset press, big solids can turn out uneven, but some digital presses are more likely to produce pronounced stripes called banding.
Fine lines, especially curved ones, can look jagged in four-color process printing, since each line must be comprised entirely of four colors of dots.
A line weight of 1 point or greater will usually be OK. No, a 0.5-point line will not be OK. (My favorite designers love 0.5-point lines!)
Doing ‘Tower Math’
Each ink color used on an offset press requires a separate ink unit or tower. Mid-size presses often have five to six towers, and small ones can have as few as one or two.
Digital presses work a little differently, but most of them print only in the four process colors, in ink or toner. (The newest HP Indigo presses can also print a limited selection of spot colors.) Each pass for a double-bump requires a separate tower.
OK, so here’s where Tower Math comes in. For this example, pretend we have access to this five-tower press. Let’s say your design includes full-color photos. You’ll need four towers for them – C, M, Y, and K.
What if you want to add a spot green? That’s one more tower. Then you want a spot varnish over the photos. Oops! 4 + 1 + 1 = 6! Too bad, you already used all available towers at five! The spot green would need to be a process build instead, or you’d need a press with more units/towers.
Not to make things more confusing, but it’s important to know that many presses are equipped with a coater, which is not the same thing as a tower. Coaters are used to apply flood coatings, such as varnish or aqueous coatings. Printers often describe their press as, “five-color plus coater.”
If a coater is part of the equation, it changes the tower math, usually for the better!
Disaster Avoidance Tips
You’d be surprised how many people don’t consider the design’s end use from the beginning.
For example, if you plan to print a quick, small run on a digital press, design with its limitations in mind, avoiding big solids or adding noise or pattern to them to de-emphasize banding, and fattening up rules to lessen jaggies.
Or if you know that your design will be reproduced in magazines – nearly always printed in four-color process – be sure to select colors that will reproduce well as builds.
Do not go by how colors look on your monitor!
Printed color and RGB color are not the same, and most monitors are not calibrated anyway. You’ll need to look at proofs (for CMYK) to see how the ink colors will really look on paper.
Before deciding whether to print with CMYK or spot color inks, it’s wise to review samples produced with the method and the press you are considering. Did designs with elements similar to yours print well?
[ Editor’s Note: Get a free Sample Kit from 48HourPrint.com. ]
Examine the samples for variations in hue, even saturation and coverage on solids, smoothness of fine lines. And of course, talk with your print reps and discuss your design with them.
When it comes to color reproduction, there are myriad factors to consider. I’ve been able to cover just some of them here, but I hope you will find this article helpful.