DIGITAL HALFTONES

COLOR DIGITAL HALFTONING

Most of our discussion of digital halftoning uses black and white illustrations only. The various black and white illustrations show how halftoning is applied to a single channel of color. By showing just one channel, we hope to make the halftoning method more clear. On this page, we've halftoned some color images using CMY color channels, and show the effect of combining the halftoned channels together.

The grayscale gradient in illustration 1 has been halftoned using a dispersed dot method, with equal amounts of CMY colors, which when combined produce a neutral gray.

The continuous tone color image in illustration 2 is shown in illustration 3 after being halftoned using a dispersed dot method for each individual color channel.

Illustration 2: Continuous Tone

Illustration 3: Dispersed Dot or "FM" Halftone

Because the dots shown in the Clustered Dot PostScript Screen illustration below are aligned in rows, care must be taken to avoid "moiré" or "screen door effect" when combining multiple screens for color printing. Careful adjustments to screen rotation and LPI should be made for this purpose.