Brightness

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For the folk album, see 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.

1 Terminology
2 Brightness of sounds
3 See also
4 Notes
5 External links

[edit] Terminology

"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.^[1]

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 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):^[2]

$\mu = {R + G + B \over 3 }$

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.

[edit] Brightness of sounds

The term "brightness" is also used in discussions of sound timbres, in a rough analogy with visual brightness. Timbre researchers consider brightness to be one of the perceptually strongest distinctions between sounds^[3], 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.

[edit] See also

[edit] Notes

^ “Brightness” in Federal Standard 1037C, the Federal Glossary of Telecommunication Terms (1996)
^ 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)."
^ D. Wessel, Timbre space as a musical control structure, Computer Music Journal, 3 (1979), pp. 45–52.