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} |} In photography, painting, and other visual arts, middle gray or middle grey is a tone that is perceptually about halfway between black and white on a lightness scale; in photography, it is typically defined as 18% reflectance in visible light. This gray reflects exactly 1/5th the number of photons per square unit as compared to a reference white of 90% reflectance.〔Woods, Mark. ''(How to Effectively Use the Gray Card )''. cameraguild.com〕 Middle gray is the universal measurement standard in photographic cameras. To calibrate light meters, whether in a camera or hand held, the 18% gray card was conceived. It is assumed that the measurement taken by a meter gives the exposure for a shot so that some of the light reflected by the object measured is equivalent to middle gray. However, many note that modern cameras generally treat 12-13% gray as "middle gray". In the sRGB color space, CIELAB middle gray is equivalent to 46.6% brightness. In 24-bit color, this is rounded to RGB value (119,119,119) or #777777.〔http://www.brucelindbloom.com/index.html?ColorCalculator.html〕 ==History== In the Zone System of Ansel Adams, middle gray is known as "Zone V" in the scale of 11 zones from Zone 0 (black) to Zone X (white). As early as 1903, middle gray was defined as the geometric mean intensity between a white and a black intensity that are in a ratio of 60:1. That is equivalent to 12.9% of the white intensity. 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「Middle gray」の詳細全文を読む スポンサード リンク
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