Moire

A white moire fabricFabric, especially silk, rayon, linen, or another material with a wavy or rippled pattern or texture impressed into its surface by engraved rollers. a red moire fabricOriginally moir? was a mohair fabric with this lustrous finish. ("Moir?" was first a French word that was probably a modification of the English word "mohair.") This kind of fabric is also called "watered," as in "watered silk." The water reference is to moir?'s resemblance to gentle waves on water. The process of producing these products has nothing to do with water.(pr. MWAH-ray)Another example:Agostino Lauro (Italian, 1861-1924), Sofa, 1900-1901, mahogany with silk moir?, the Mitchell Wolfson Jr. Collection, The Wolfsonian-Florida International U, Miami Beach, FL.When materials with repetitive lines overlap, moir? patterns result. Several phenomena occur in the overlapping of repetitive layers, whether monochrome or moire pattern generated by one line pattern overlaid on anotherpolychrome, periodic or non-periodic. Moving one pattern over another can generate fascinating optical effects.We see these effects when looking through two sets of similar screen or fence materials, and their patterns are not perfectly aligned. An even handier demonstration of this phenomenon can be observed while overlapping two combs. See an animated demonstration of a moir? fringe pattern ? a shadow moir?: one of the patterns is a shadow of the other pattern.Moir? is also found in interference of multiple dot-grid textures of halftone patterned images ? an allover murky, herringbone or crosshatched or dotted pattern. Generally unwanted, these patterns result from two uses of a picture with a halftone pattern (a strong magnifying glass will show it, whether B&W or CMYK); as a moire pattern appearing in a scanned halftone imagewhen such a picture is reproduced, whether by analog or by digital means. Beware, for instance, of scanning halftone pictures printed in magazines, newspapers, calendars, postcards, etc. (not to mention the copyright issue, a serious consideration in itself). Moir? patterns often appear all over such scans, caused by interference between the first set(s) of fine pattern halftone grids (133 or 150 lpi) and the grid of pixels created in a digital version of the picture (300 or 600 dpi scanner CCD array). These combine into maximums or minimums every several pixels in the image, depending on the spacing of the dots. This affects the overall light intensity in periodic patterns that become very visible. Moir? effects can be diminished by the use of sharpening and unsharpening filters.Also see analog-to-digital conversion, curve, Art Nouveau, digital image, image resolution, output resolution, and straight.