brightness


Also found in: Dictionary, Thesaurus, Medical, Legal, Acronyms, Wikipedia.
Related to brightness: brightness control, Brightness temperature

brightness

The intensity of light or other radiation emitted from – absolute or intrinsic brightness – or received from – apparent brightness – a celestial body, the latter decreasing as the distance from the body increases. Intrinsic brightness is directly related to the luminosity of a body in a given spectral region. Apparent brightness is considered in terms of apparent magnitude: a star one magnitude less than another is about 2.5 times brighter. If two stars belong to the main sequence then the brighter star is the hotter of the two. See also radio brightness.

Brightness

The amount of light energy reflected from a surface. The degree of brightness depends on the color value and texture on its surface. The surface brightness of a task should be the same as its background or brighter. The maximum brightness ratio should be 3:1, and the brightness between the task and the darkest background area should be 5:1 to avoid objectionable glare.

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

brightness

[′brīt·nəs]
(optics)
The characteristic of light that gives a visual sensation of more or less light.

brightness

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

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]

brightness

(graphics)
(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.

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.
References in classic literature ?
The objects that had made a shadow hitherto, embodied the brightness now.
I'm not envious: I never feel hurt at the brightness of Isabella's yellow hair and the whiteness of her skin, at her dainty elegance, and the fondness all the family exhibit for her.
Although she was now in her forty-fourth year; although she had been tried, in bygone times, by the premature loss of more than one of her children, and by long attacks of illness which had followed those bereavements of former years -- she still preserved the fair proportion and subtle delicacy of feature, once associated with the all-adorning brightness and freshness of beauty, which had left her never to return.
The summer light struck into the corner brilliantly in the earlier part of the day; but, when the streets grew hot, the corner was in shadow, though not in shadow so remote but that you could see beyond it into a glare of brightness.
The brightness of the shops where holly sprigs and berries crackled in the lamp heat of the windows, made pale faces ruddy as they passed.
The walls were whitewashed as white as milk, and the patchwork counterpane made my eyes quite ache with its brightness.
I saw that the bride within the bridal dress had withered like the dress, and like the flowers, and had no brightness left but the brightness of her sunken eyes.
By this time, however, the ladies had pressed forward, curious to know what could have brought the solitary linen-weaver there under such strange circumstances, and interested in the pretty child, who, half alarmed and half attracted by the brightness and the numerous company, now frowned and hid her face, now lifted up her head again and looked round placably, until a touch or a coaxing word brought back the frown, and made her bury her face with new determination.
I could sleep little that night, because of the sorrow at my heart, but sat awake looking, in the brightness of the moon, upon the grey face of the stone Witch, and on the depths of the forest that grew about her knees, wondering the while if the bones of Umslopogaas lay broken in that forest.
There was a soft brightness in their faces, as though rain had fallen in the night; but it was the warm sweet rain of joy that brings the flowers, and is but sister to the sun.
Thus far these beyond Compare of mortal prowess, yet observ'd Thir dread Commander: he above the rest In shape and gesture proudly eminent Stood like a Towr; his form had yet not lost All her Original brightness, nor appear'd Less then Arch Angel ruind, and th' excess Of Glory obscur'd: As when the Sun new ris'n Looks through the Horizontal misty Air Shorn of his Beams, or from behind the Moon In dim Eclips disastrous twilight sheds On half the Nations, and with fear of change Perplexes Monarchs.
Just then a sort of brightness fell upon me in the barrel, and looking up, I found the moon had risen and was silvering the mizzen-top and shining white on the luff of the fore-sail; and almost at the same time the voice of the lookout shouted, "Land ho