" and spelled "moiré." In computer graphics, a visible distortion. It results from a variety of conditions; for example, when scanning halftones at a resolution not consistent with the eventual printed resolution or when superimposing curved patterns on one another. Internal monitor misalignment can also be a cause. The term comes from the French "moirer" (to water) and is used to express a rippled, water-like look, which is often a desired artistic effect.
A Common Moiré Pattern
Reducing images with checkered or herringbone patterns often creates the Moiré look as in the above example. At the top, the pillow reduces correctly but the checkered fabric in the chair creates a swirling Moiré effect.
When printing halftones, rosettes are formed if the screens are registered properly. The magnified view at the bottom shows the misaligned rosettes, which actually create the Moiré pattern. (Images courtesy of Adobe Systems, Inc.)