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Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light.〔(Merriam-Webster.com ) Merriam-Webster Dictionary definition of bright〕 In other words, brightness is the perception elicited by the luminance of a visual target. This is a subjective attribute/property of an object being observed and one of the color appearance parameters of color appearance models. Brightness refers to an absolute term and should not be confused with Lightness.〔() Brightness vs. Lightness 〕 ==Terminology== The adjective ''bright'' derives from an Old English ''beorht'' with the same meaning via metathesis giving Middle English ''briht''. The word is from a Common Germanic *', ultimately from a PIE root with a closely related meaning, *' "white, bright". "Brightness" was formerly used as a synonym for the photometric term ''luminance'' and (incorrectly) for the radiometric term ''radiance''. As defined by the US ''Federal Glossary of Telecommunication Terms'' (FS-1037C), "brightness" should now be used only for non-quantitative references to physiological sensations and perceptions of light.〔“(Brightness )” in Federal Standard 1037C, the ''Federal Glossary of Telecommunication Terms'' (1996)〕 A given target luminance can elicit different perceptions of brightness in different contexts; see, for example, White's illusion. In the RGB color space, brightness can be thought of as the arithmetic mean ''μ'' of the red, green, and blue color coordinates (although some of the three components make the light seem brighter than others, which, again, may be compensated by some display systems automatically):〔(What are HSB and HLS? ), Charles Poynton: "The usual formulation of HSB and HLS compute so-called "lightness" or "brightness" as (''R'' + ''G'' + ''B'')/3. This computation conflicts badly with the properties of colour vision, as it computes yellow to be about six times more intense than blue with the same "lightness" value (say ''L'' = 50)."〕 : Brightness is also a color coordinate in the HSB or HSV color space (hue, saturation, and brightness or value). With regard to stars, brightness is quantified as apparent magnitude and absolute magnitude. Brightness is, at least in some respects, the antonym of darkness. 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「brightness」の詳細全文を読む スポンサード リンク
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