Brightness (redirected from Brigthness)

brightness

The black level of a display screen. Although it may sound peculiar, the brightness adjusts the "black level" of the display system (how black the black is). See contrast.

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brightness [′brīt·nəs]

(optics)

The characteristic of light that gives a visual sensation of more or less light.

luminance

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brightness

That attribute of visual perception in accordance with which a surface appears to emit more light or less light. Now called luminance.

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Brightness

Alpha Centauri

brightest star in Centaurus constellation; closest star to Earth. [Astronomy: NCE, 74]

diamond

April birthstone, most reflective of gems. [Gem Symbolism: Jobes, 440–441]

North Star

bright star visible to naked eye and nearest to the north celestial pole. [Astronomy: EB, VIII: 79]

Sirius

dog star; brightest star in the heavens. [Astronomy: EB, IX: 238]

St. Elmo’s fire

glow of electrical discharge appearing on towers and ships’ masts. [Physics: EB, VIII: 780]

Venus

bright planet, second from the Sun. [Astronomy: EB, X: 392]

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(graphics)

brightness - (Or "tone", "luminance", "value", "luminosity", "lightness") The coordinate in the HSB colour model that determines the total amount of light in the colour. Zero brightness is black and 100% is white, intermediate values are "light" or "dark" colours. The other coordinates are hue and saturation.

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Brightness 

(also surface brightness), in astronomy, a characteristic of the emittance or reflectance of the surface of a celestial body. The brightness of faint celestial sources is expressed in terms of the number of stars of a given stellar magnitude in an area measuring 1 square second of arc (arcsec²), 1 square minute of arc (arcmin²), or 1 square degree (deg²). In other words, the illuminance from such an area is compared with the illuminance produced by a star of known stellar magnitude.

The brightness of the moonless night sky in clear weather, which is equal to 2 × 10^–8 stilbs (sb), is characterized by one star of stellar magnitude 22.4 per arcsec², or one star of stellar magnitude 4.61 per deg². The brightness of an average nebula is equal to one star of stellar magnitude 19–20 per arcsec². The brightness of Venus is equal to about one star of stellar magnitude 3 per arcsec². The brightness of an area of 1 arcsec² over which the light of a zero-magnitude star is distributed is equal to 9.25 sb. The brightness of the center of the solar disk is equal to 150,000 sb; that of the full moon, to 0.25 sb.

A surface for which the brightness does not depend on the angle of inclination of the area to the line of sight is said to be orthotropic. The flux emitted by such a surface behaves in accordance with Lambert’s law and is called the luminance. The unit of luminance is the lambert, which corresponds to a total flux of 1 lumen/cm².

D. IA. MARTYNOV