Editing Moiré pattern (section)

=== Printing full-color images ===
[[File:BeatTrackMoirePattern.ogg|thumb|upright=1.5|
'''Warning: audiogenic [[epileptic seizure]] hazard.''' The product of two "beat tracks" of slightly different speeds overlaid, producing an audible moiré pattern; if the beats of one track correspond to where in space a black dot or line exists and the beats of the other track correspond to the points in space where a camera is sampling light, because the frequencies are not exactly the same and aligned perfectly together, beats (or samples) will align closely at some moments in time and far apart at other times. The closer together beats are, the darker it is at that spot; the farther apart, the lighter. The result is periodic in the same way as a graphic moiré pattern. See: [[phasing (music)|phasing]].]]
In [[graphic arts]] and [[prepress]], the usual technology for printing full-color images involves the superimposition of [[halftone]] screens. These are regular rectangular dot patterns—often four of them, printed in cyan, yellow, magenta, and black. Some kind of moiré pattern is inevitable, but in favorable circumstances the pattern is "tight"; that is, the spatial frequency of the moiré is so high that it is not noticeable. In the graphic arts, the term ''moiré'' means an ''excessively visible'' moiré pattern. Part of the prepress art consists of selecting screen angles and halftone frequencies which minimize moiré. The visibility of moiré is not entirely predictable. The same set of screens may produce good results with some images, but visible moiré with others.