Brightness 40818 212415679 2008-05-14T19:08:23Z Neelix 1169106 Added link to album {{for|the folk album|The Brightness}} '''Brightness''' (also called '''effulgence''') is an attribute of [[visual perception]] in which a source appears to emit a given amount of [[light]]. 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. ==Terminology== "Brightness" was formerly used as a synonym for the [[photometry (optics)|photometric]] term ''[[luminance]]'' and (incorrectly) for the [[radiometric]] term ''[[radiance]]''. As defined by the US ''Federal Glossary of Telecommunication Terms'' ([[Federal Standard 1037C|FS-1037C]]), "brightness" should now be used only for non-quantitative references to physiological sensations and perceptions of light.<ref>“[http://www.its.bldrdoc.gov/fs-1037/dir-005/_0719.htm Brightness]” in Federal Standard 1037C, the ''Federal Glossary of Telecommunication Terms'' (1996)</ref> A given target luminance can elicit different perceptions of brightness in different contexts; see, for example, [[White's illusion]] and [[Wertheimer]]-Benary illusion. In the [[RGB color space]], brightness can be thought of as the [[arithmetic mean]] ''&mu;'' of the '''R'''ed, '''G'''reen, and '''B'''lue 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):<ref>[http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC36 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)."</ref> :<math>\mu = {R + G + B \over 3 }</math> Brightness is also a color coordinate in the HSB or [[HSV color space]] (hue, [[Saturation (color theory)|saturation]], and brightness or value). With regard to [[star]]s, brightness is quantified as [[apparent magnitude]] and [[absolute magnitude]]. ==Brightness of sounds== The term "brightness" is also used in discussions of sound [[timbre]]s, in a rough analogy with visual brightness. Timbre researchers consider brightness to be one of the perceptually strongest distinctions between sounds<ref>D. Wessel, [http://mediatheque.ircam.fr/articles/textes/Wessel78a/ Timbre space as a musical control structure], Computer Music Journal, 3 (1979), pp. 45–52.</ref>, and formalize it acoustically as an indication of the amount of high-frequency content in a sound, using a measure such as the [[spectral centroid]]. ==See also== * [[Luma (video)]] * [[Luminance (relative)]] ==Notes== {{reflist}} ==External links== {{Wiktionarypar|brightness}} * [http://www.poynton.com/ColorFAQ.html Poynton's Color FAQ] [[Category:vision]] [[Category:Photometry]] [[bg:Яркост]] [[de:Helligkeit]] [[ko:명도]] [[it:Luminosità (teoria dei colori)]] [[hu:Világosság]] [[pt:Brilhância]] [[th:ความสว่าง]] [[vi:Độ trắng]] [[zh:明度]]