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Brightness is an attribute of
visual perception
Visual perception is the ability to interpret the surrounding environment through photopic vision (daytime vision), color vision, scotopic vision (night vision), and mesopic vision (twilight vision), using light in the visible spectrum reflecte ...
in which a source appears to be radiating or reflecting
light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
. In other words, brightness is the
perception
Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system ...
elicited by the
luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls withi ...
of a visual target. The perception is not linear to luminance, and relies on the context of the viewing environment (for example, see
White's illusion
White's illusion is a brightness illusion where certain stripes of a black-and-white grating are partially replaced by a gray rectangle (see the figure). Both of the gray bars of A and B have the same color and opacity. The brightness of the gray ...
).
Brightness is a subjective sensation of an object being observed and one of the
color appearance parameters of many
color appearance model
A color appearance model (CAM) is a mathematical model that seeks to describe the perceptual aspects of human color vision, i.e. viewing conditions under which the appearance of a color does not tally with the corresponding physical measurement of ...
s, typically denoted as
. Brightness refers to how much light ''appears to shine'' from something. This is a different perception than
lightness
Lightness is a visual perception of the luminance (L) of an object. It is often judged relative to a similarly lit object. In colorimetry and color appearance models, lightness is a prediction of how an illuminated color will appear to a stan ...
, which is how light something appears ''compared to'' a similarly lit white object.
The adjective ''
bright
Bright may refer to:
Common meanings
*Bright, an adjective meaning giving off or reflecting illumination; see Brightness
*Bright, an adjective meaning someone with intelligence
People
* Bright (surname)
* Bright (given name)
*Bright, the stage na ...
'' derives from an Old English ''
beorht Bert is a hypocoristic form of a number of various Germanic male given names, such as Robert, Albert, Elbert, Herbert, Hilbert, Hubert, Gilbert, Wilbert, Filbert, Norbert, Osbert, Bertram, Berthold, Bertrand, Umberto, Humbert, Cuthbert, Delber ...
'' with the same meaning via metathesis giving Middle English ''briht''. The word is from a
Common Germanic
Proto-Germanic (abbreviated PGmc; also called Common Germanic) is the reconstructed proto-language of the Germanic branch of the Indo-European languages.
Proto-Germanic eventually developed from pre-Proto-Germanic into three Germanic branc ...
', ultimately from a
PIE
A pie is a baked dish which is usually made of a pastry dough casing that contains a filling of various sweet or savoury ingredients. Sweet pies may be filled with fruit (as in an apple pie), nuts ( pecan pie), brown sugar ( sugar pie), swe ...
root with a closely related meaning, *' "white, bright".
"Brightness" was formerly used as a synonym for the
photometric term ''
luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls withi ...
'' and (incorrectly) for the
radiometric
Radiometry is a set of techniques for measuring electromagnetic radiation, including visible light. Radiometric techniques in optics characterize the distribution of the radiation's power in space, as opposed to photometric techniques, which cha ...
term ''
radiance
In radiometry, radiance is the radiant flux emitted, reflected, transmitted or received by a given surface, per unit solid angle per unit projected area. Radiance is used to characterize diffuse emission and reflection of electromagnetic radiatio ...
''. As defined by the US ''Federal Glossary of Telecommunication Terms'' (
FS-1037C
Federal Standard 1037C, titled Telecommunications: Glossary of Telecommunication Terms, is a United States Federal Standard issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, a ...
), "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)
With regard to
star
A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
s, brightness is quantified as
apparent magnitude
Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...
and
absolute magnitude
Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...
.
Brightness is an antonym of
dimness or dullness.
New meaning
The United States
Federal Trade Commission
The Federal Trade Commission (FTC) is an independent agency of the United States government whose principal mission is the enforcement of civil (non-criminal) antitrust law and the promotion of consumer protection. The FTC shares jurisdiction ov ...
(FTC) has assigned an unconventional meaning to brightness when applied to
lamps. When appearing on light bulb packages, brightness means
luminous flux
In photometry, luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of electromagnetic radiation (including infrared, ultraviolet, and visible light), in th ...
, while in other contexts it means luminance.
Luminous flux is the total amount of light coming from a source, such as a lighting device. Luminance, the original meaning of brightness, is the amount of light per solid angle coming from an area, such as the sky. The table below shows the standard ways of indicating the amount of light.
See also
*
Brightness (sound)
In music, timbre ( ), also known as tone color or tone quality (from psychoacoustics), is the perceived sound quality of a musical note, sound or tone. Timbre distinguishes different types of sound production, such as choir voices and musical ...
*
Luma (video)
In video, luma represents the brightness in an image (the "black-and-white" or achromatic portion of the image). Luma is typically paired with chrominance. Luma represents the achromatic image, while the chroma components represent the color infor ...
*
Luminance (relative)
Relative luminance Y follows the photometric definition of luminance L including spectral weighting for human vision, but while luminance L is a measure of light in units such as cd/m^2, Relative luminance Y values are normalized as 0.0 to 1.0 ...
*
Luminosity
Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a st ...
* The difference between luminescence and brightness is practically exploited by
prism lighting
Prism lighting is the use of prisms to improve the distribution of light in a space. It is usually used to distribute daylight, and is a form of anidolic lighting.
Prism lighting was popular from its introduction in the 1890s through to the 19 ...
Notes
External links
Poynton's Color FAQ
{{Authority control
Vision
Photometry
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