A while back I wrote about color and pigment in inks and paints (Copper Plate Daily – October 10 2009). I have been thinking lately about the differences between mixing colored inks and using process color.

For those of you that are unfamiliar with the term, process color is the mechanism of creating color on a substrate by printing dots of carefully chosen primary colors in close proximity and allowing optical mixing (the tendency of the eye to blend colors) to create the final perceived color. Pick up a magazine with a color photo and you are looking at an example of process color. Traditional commercial printing uses 4 primaries for this purpose (Cyan, Magenta, Yellow and Black) and is referred to as CMYK color.

If you have ever seen a painting in person that you have seen reproduced in a book, you were probably struck by the difference in the vibrancy (and subtlety) of the colors. This points up one of the essential limitations of process color: a restricted color gamut. Simply put, a gamut is the volume of the total color space that can be represented by a color system. For any set of pigments (under a given lighting condition) there are some colors that cannot be achieved. These are referred to as being outside the gamut.

The gamut of a process color system system depends on the the set of primary pigments chosen, the halftone dot size, dot spacing, ink film thickness, substrate reflectivity and substrate absorbency (among others).

The increasing sophistication of inkjet printing technology is improving the performance of process color. High end printers now use more primary colors, allow smaller, more closely spaces dots, etc. The results are impressive.

In contrast, mixing and printing with colored inks has very different color affects. At the lowest level, optical mixing is still taking place, but the ‘dot size’ is now the pigment particle size. The more colors in the the printmakers ‘pallet’, the wider the effective gamut. Add in various whites, blacks, tint bases, film thicknesses, print order, and more and you have an astonishing range of color subtlety available. More ‘paint like’ if you will, just not normally applied with a brush.

This is not to suggest that process color is bad. It simply is. Like any set of processes and materials, it has a range of possibilities and limitations.