process color
A printing process which uses four specific colored inks: cyan, magenta, yellow and black (CMYK), and halftone printing plates, to reproduce a range of colors.
process color: CMYK printing that fakes full color
Process color printing uses four inks, cyan, magenta, yellow, and black (CMYK), applied in sequence through separate printing plates to create the full spectrum of colors. Each ink layer is applied at different screen angles, typically 45 degrees apart, to minimize visible moiré patterns. The black ink, called key, strengthens shadows and ensures crisp detail where the three process colors alone would produce muddy tones.
The illusion of continuous color comes from halftoning. Rather than laying down solid ink, each plate prints tiny dots at varying sizes and spacing. When printed wet-on-wet on most substrates, these dots sit close enough that the human eye blends them from normal viewing distance. A typical halftone screen uses 65 to 175 lines per inch for sheetfed lithography, though publication work may reach 300 lpi. Newsprint traditionally used coarser screens around 65 to 85 lpi because the substrate cannot hold fine detail.
Process color is economical for high-volume reproduction of photographic images and continuous-tone artwork. A single four-color press in offset lithography can produce 5000 to 20000 impressions per hour. The method works on paper, cardboard, and film, but struggles with certain substrates. Uncoated newsprint shows dot gain, where dots swell on contact with the absorbent surface, flattening colors. Gloss coated stock minimizes this, holding tight dot structure.
Color separation and limitations
The workflow begins with color separation: a color original is scanned or photographed and digitally decomposed into its four color channels. Skilled pressmen then match ink density and hue angle during makeready because CMYK cannot perfectly reproduce all colors visible to the human eye. Bright, saturated hues and spot colors outside the gamut will appear duller. This is why high-end packaging and brand identity work often supplement process color with spot inks.
Registration accuracy determines print quality. If cyan, magenta, and yellow plates misalign by more than 0.003 inches on coated stock, color fringing becomes visible and halftone dots fail to merge properly. Presses use registration marks, mechanical gripers, and registration sensors to hold tolerance. Even small slippage compounds across the print run, which is why long runs on vintage equipment often show edge effects.