TheInfoList

Brightness is an attribute of
visual perception Visual perception is the ability to interpret the surrounding environment (biophysical), environment through photopic vision (daytime vision), color vision, scotopic vision (night vision), and mesopic vision (twilight vision), using light in ...
in which a source appears to be radiating or reflecting
light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400â€“700 nan ...

. In other words, brightness is the perception elicited by the
luminance Luminance is a photometricPhotometry can refer to: * Photometry (optics), the science of measurement of visible light in terms of its perceived brightness to human vision * Photometry (astronomy), the measurement of the flux or intensity of an ...

of a visual target. It is not necessarily proportional to luminance. This is a subjective attribute/property of an object being observed and one of the color appearance parameters of
color appearance model #REDIRECT Color appearance model A color appearance model (CAM) is a mathematical model that seeks to describe the perception, perceptual aspects of human color vision, i.e. viewing conditions under which the appearance of a color does not tally wi ...
s. Brightness refers to an absolute term and should not be confused with
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 stand ...

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 name ...
'' derives from an Old English ''
beorhtBert is a hypocoristic A hypocorism ( or ; from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly d ...
'' 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 Reconstruction may refer to: Politics, history, and sociology *Reconstruction (law), the transfer of a company's (or several companies') business to a new ...
', ultimately from a
PIE A pie is a baked Baking is a method of preparing food that uses dry heat, typically in an oven, but can also be done in hot ashes, or on hot stones. The most common baked item is bread but many other types of foods are baked. Heat is grad ...
root with a closely related meaning, *' "white, bright". "Brightness" was formerly used as a synonym for the
photometricPhotometry can refer to: * Photometry (optics), the science of measurement of visible light in terms of its perceived brightness to human vision * Photometry (astronomy), the measurement of the flux or intensity of an astronomical object's electroma ...
term ''
luminance Luminance is a photometricPhotometry can refer to: * Photometry (optics), the science of measurement of visible light in terms of its perceived brightness to human vision * Photometry (astronomy), the measurement of the flux or intensity of an ...

'' and (incorrectly) for the
radiometric Radiometry is a set of techniques for measuring Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. The scope and application of measurement are dependent on the ...
term ''
radiance In radiometry Radiometry is a set of techniques for measuring Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. The scope and application of measurement are ...
''. 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. A given target luminance can elicit different perceptions of brightness in different contexts; see, for example,
White's illusion White's illusion is a brightness illusion An illusion is a distortion of the senses, which can reveal how the human brain The human brain is the central organ (anatomy), organ of the human nervous system, and with the spinal cord makes up th ...
. In an
RGB color space An RGB color space is any additive Additive may refer to: Mathematics * Additive function In number theory, an additive function is an arithmetic function ''f''(''n'') of the positive integer ''n'' such that whenever ''a'' and ''b'' are copr ...
, brightness can be thought of as the
arithmetic mean In mathematics Mathematics (from Greek: ) includes the study of such topics as numbers (arithmetic and number theory), formulas and related structures (algebra), shapes and spaces in which they are contained (geometry), and quantities and t ...
''Î¼'' of the red, green, and blue color coordinates (although some of the three components make the light seem brighter than others, which, again, ):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)." :$\mu =$ Brightness is also a color coordinate in
HSL color space HSL (hue, saturation, lightness) and HSV (hue, saturation, value, also known as HSB or hue, saturation, brightness) are alternative representations of the RGB color model, designed in the 1970s by computer graphics researchers to more closely align ...
:
hue In color theory In the visual arts The visual arts are art forms such as painting Painting is the practice of applying paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after applica ...

, saturation, and lightness, meaning here brightness. With regard to
star A star is an astronomical object consisting of a luminous spheroid of plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral) or heliotrope, a mineral aggregate * Quarkâ ...

s, brightness is quantified as 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 ma ...
. Brightness is, at least in some respects, the antonym of
darkness Darkness, the direct opposite of lightness, is defined as a lack of lighting, illumination, an absence of visible spectrum, visible light, or a surface that absorbs light, such as black or brown. Human visual perception, vision is unable to di ...

.

# New meaning

The United States
Federal Trade Commission The Federal Trade Commission (FTC) is an independent agency of the United States government Independent agencies of the United States federal government The federal government of the United States (U.S. federal government or U.S. gover ...

(FTC) has assigned an unconventional meaning to brightness when applied to
lamps Lamp, Lamps or LAMP may refer to: Lighting * Oil lamp, using an oil-based fuel source * Kerosene lamp, using kerosene as a fuel * Electric lamp, or light bulb, a replaceable component that produces light from electricity * Light fixture, or light ...
. When appearing on light bulb packages, brightness means
luminous flux In photometryPhotometry can refer to: * Photometry (optics), the science of measurement of visible light in terms of its perceived brightness to human vision * Photometry (astronomy), the measurement of the flux or intensity of an astronomical ...

, 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.

* Brightness (sound) *
Luma (video) In video Video is an electronic Electronic may refer to: *Electronics Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matter. It uses ...
*
Luminance (relative) Relative luminance follows the photometric definition of luminance, but with the values normalized to 1 or 100 for a reference white. Like the photometric definition, it is related to the luminous flux density in a particular direction, which is ...
*
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 s ...