Ed #2 Quadtones

Halftone images begin with the fact that most presses use an on-off principle. They either apply or withhold ink, with no middle steps. To recreate the continuous tones that are seen by the human eye, the image to be printed is separated by a screen into countless tiny dots that are blended by the eye to create an illusion of continuous tone, even though the press still only applies or withholds ink.

In a conventional black and white or one-color image, the white or light gray images are formed by tiny black dots separated by considerable white space–the unprinted surface of the paper. Darker tones, or shadow areas, are made with larger black dots separated by less white space.