Brightness

Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light.1 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.

Contents

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.2

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):3

\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.

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 sounds4, 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

Notes

  1. ^ Merriam-Webster.com Merriam-Webster Dictionary definition of bright
  2. ^ “Brightness” in Federal Standard 1037C, the Federal Glossary of Telecommunication Terms (1996)
  3. ^ 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)."
  4. ^ D. Wessel, Timbre space as a musical control structure, Computer Music Journal, 3 (1979), pp. 45–52.

External links

Look up brightness in Wiktionary, the free dictionary.

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  • This page was last modified on 27 December 2008, at 05:39.

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