moiré

Definition: Apparent pattern of alternating light and dark lines or rings seen when two or more regular patterns are superimposed. * It results from the interaction of two regular patterns such that where dark lines of the two patterns are superimposed, the resulting pattern looks bright, and where the dark lines lie between each other, the pattern looks dark: over a distance this alternates at a frequency related to the difference between the frequencies of the two patterns. * Moiré is seen when e.g. stripes on a shirt are imaged on a TV screen. There's more to it Moiré may seem to be one of those obscurities scientists come up with to justify their research grants, but is now recognised as one of the fundamental problems with digital imaging. As the sensor array is regular, moiré can occur as soon as you point a digital camera at a regular pattern -- stripey clothes, fences, rows of seats, etc. Solving the problem is horribly difficult: you can try software methods (very tricky) or extremely expensive hardware solutions such as anti-aliasing filters.

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