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Halftone is the reprographic technique that simulates continuous tone imagery through the use of dots, varying either in size or in spacing, thus generating a gradient like effect.〔Campbell, Alastair. The Designer's Lexicon. ©2000 Chronicle, San Francisco.〕 "Halftone" can also be used to refer specifically to the image that is produced by this process.〔 Where continuous tone imagery contains an infinite range of colors or greys, the halftone process reduces visual reproductions to an image that is printed with only one color of ink, in dots of differing size (amplitude modulation) or spacing (frequency modulation). This reproduction relies on a basic optical illusion: the tiny halftone dots are blended into smooth tones by the human eye. At a microscopic level, developed black-and-white photographic film also consists of only two colors, and not an infinite range of continuous tones. For details, see film grain. Just as color photography evolved with the addition of filters and film layers, color printing is made possible by repeating the halftone process for each subtractive color—most commonly using what is called the "CMYK color model".〔McCue, Claudia. Real World Print Production. ©2007, Peachpit Berkeley.〕 The semi-opaque property of ink allows halftone dots of different colors to create another optical effect—full-color imagery.〔 ==History== William Fox Talbot is credited with the idea of halftone printing. In the early 1830s, he suggested using "photographic screens or veils" in connection with a photographic intaglio process.〔Twyman, Michael. Printing 1770–1970: an illustrated history of its development and uses in England. Eyre & Spottiswoode, London 1970.〕 Several different kinds of screens were proposed during the following decades. One of the well known attempts was by Stephen H. Horgan while working for the ''New York Daily Graphic''. The first printed photograph was an image of Steinway Hall in Manhattan published on December 2, 1873.〔''LIFE''. "100 Photographs That Changed the World". Time, Inc. August 25, 2003, p 18.〕 The ''Graphic'' then published "the first reproduction of a photograph with a full tonal range in a newspaper" on March 4, 1880 (entitled "A Scene in Shantytown") with a crude halftone screen.〔Meggs, Philip B. A History of Graphic Design. John Wiley & Sons, Inc. 1998. p 141. ISBN 0-471-29198-6.〕 The first truly successful commercial method was patented by Frederic Ives of Philadelphia in 1881.〔〔 Although he found a way of breaking up the image into dots of varying sizes, he did not make use of a screen. In 1882, the German Georg Meisenbach patented a halftone process in England. His invention was based on the previous ideas of Berchtold and Swan. He used single lined screens which were turned during exposure to produce cross-lined effects. He was the first to achieve any commercial success with relief halftones.〔 Shortly afterwards, Ives, this time in collaboration with Louis and Max Levy, improved the process further with the invention and commercial production of quality cross-lined screens.〔 The relief halftone process proved almost immediately to be a success. The use of halftone blocks in popular journals became regular during the early 1890s.〔 The development of halftone printing methods for lithography appears to have followed a largely independent path. In the 1860s, A. Hoen & Co. focused on methods allowing artists to manipulate the tones of hand-worked printing stones.〔August Hoen, ''Composition for etching stone'', U.S. Patent 27,981, Apr 24, 1860.〕 By the 1880s, Hoen was working on halftone methods that could be used in conjunction with either hand-worked or photolithographic stones.〔August Hoen, ''Lithographic Process'', U.S. Patent 227,730, May 15, 1883.〕〔August Hoen, ''Lithographic Process'', U.S. Patent 227,782, May 18, 1880.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「halftone」の詳細全文を読む スポンサード リンク
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