Color conversion from PMS to CMYK can be tricky
Improvements in desktop publishing software and computer technology have made four-color process printing more
affordable. Before this many pieces were printed in one and two colors. Four-color process uses varying strengths of
standard blue (cyan), red (magenta), yellow and black (CMYK) inks to replicate many colors of the spectrum. For more
information on how four-color process works, please read more on this site.
Another way to print colors is to print a specific color of ink. Let's say you are printing a simple newsletter and you want the
headlines in red and everything else in black. The headlines would be printed in a specific red ink, identified by a PMS
(Pantone Matching System) number. This system is similar to buying paint. You select a color from a swatch. The service
person then makes your color by mixing a few base colors in varying quantities. You end up with the color that matches the
The PMS system works the same way. You select a color from a book of swatches. There are fourteen base colors that are
mixed to yield other colors. The end product is denoted by a number, say PMS 285 for instance. You could have something
printed in Chicago or Copenhagen and the color would look the same as long as they use the PMS system. This is the
familiar PMS book. You choose a color from it and the ink is mixed using base colors. The limitation to the PMS system is
that every color you want on your piece needs to be a separate color. That is impractical for reproducing a color image such
as a photograph. Thus four-color process was born. The image is broken up into varying intensities of the four CMYK
colors. When these are printed on top of one another they combine to form all of the colors in the image.
In four-color process, an image is broken up into varying intensities of four standard colors. When the four are printed over
one another they combine to form the miriad of colors in the image.
In truth, due to the amount of pigments in the base colors, four-color process can't produce all the colors you may want. As
an example, look at the cyan color in the illustration above. As you can see, it isn't very dark. When an image calls for a dark
blue, the basic building block color (cyan) isn't very dark. Therefore, dark blues have a tendency to lack vibrancy and power.
Remember, standard PMS colors have 14 base colors whereas CMYK has only four. We'll get into this more fully later in
the article. For now, just realize that CMYK can't produce all of the colors we see.
This isn't much of a problem in photographs. Most often the overall look of an image is fine. Issues arise when people
expect colors that four-color process isn't capable of producing. Take a logo for instance. Let's say a large company such
as The Home Depot wants to print its orange logo. They will specify a PMS match that can be reproduced anywhere.
However the CMYK "equivalent" of the PMS color may not match exactly. If The Home Depot is picky about its logo, this may
be a problem.
If you specify a PMS color in a piece to be printed in four-color process, the color will be converted to a CMYK mix. Changes
in color can range from subtle to substantial. See the color chart below. The swatches on the left show PMS colors. The
swatch on the right is a CMYK version, an approximation of the PMS color. As you can see, some colors convert quite well
to process and some quite poorly.
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Colors and Conversion