| 释义 |
ˈluminance
[f. next: see -ance.]
1. Luminousness.
1880Ouida Moths III. xi. 282 Her eyes have a serious sweet luminance. 1884E. A. B. Hodgetts tr. Remin. Gen. Skobeleff 322 The bright luminance of our freedom shall shine forth to be seen by the whole world. 1893M. Corelli Barabbas iii. (1894) 15 The flickering luminance thus given only making the native darkness of the place more palpable.
2. Physics. The amount of luminous flux emitted by unit area of a source into unit solid angle (the objective analogue of subjective brightness).
1950Jenkins & White Fund. Optics (ed. 2) vii. 104 To distinguish it from the visual sensation of brightness, it is usually termed the luminance in the technical literature, but..we shall use the commoner name brightness, with the understanding that..the photometric quantity..is meant. 1952Electronics Nov. 208/2 Luminance is a purely photometric quantity. Use of this name permits brightness to be used entirely with reference to the sensory response. 1957V. J. Kehoe Technique Film & Television Make-Up viii. 95 As to..the reception of a color telecast on a monochromatic receiver, only the luminance portion will be supplied to the single electron gun in the monochrome tube to produce a black-and-white version of the signal. 1968Sci. Amer. Nov. 8/2 Consider two areas that have the same luminance but one of which is seen against a dark background while the other is seen against a light background. The former will appear to be brighter. 1970Jrnl. Gen. Psychol. LXXXII. 111 Midway between these red apertures a yellow spot, three minutes of arc in diameter and 3·1 ftL in luminance, provided the fixation. 1972Sci. Amer. June 101/1 Measurements of a photograph of the vase..showed that the luminance of the moon was 15 foot-lamberts and the space one moon diameter below was 20 foot-lamberts. The contour effect is so strong that the apparent brightness of the two areas is just the reverse of the objective luminance.
Restrict Physics to sense 2 a in Dict. and add: [2.] b. Television. The component of a television signal which carries information on the brightness of the image. Also luminance signal. Cf. chrominance n.
1953Electronics Dec. 139/3 The term ‘chrominance’ refers to two signals which carry color information. These signals, when added to the luminance signal, provide the hue and saturation components of the color image. 1957V. J. Kehoe Technique Film & Television Make-up viii. 95 As to..the reception of a color telecast on a monochromatic receiver, only the luminance portion will be supplied to the single electron gun in the monochrome tube to produce a black-and-white version of the signal. 1973Sci. Amer. May 118/2 Here there is an analogy with color television, in which the luminance—the three-color sum—is transmitted separately, along with two color-difference signals, rather than three color signals directly. 1983E. Trundle Beginner's Guide Videocassette Recorders ii. 21 If we regard the FM luminance spectrum as extending from 1 MHz to 6 MHz, it is now occupying less than three octaves. 1990OnSat 29 July–4 Aug. 8/2 The luminance signal is markedly increased (from a low of 3.4 MHz to a high range of 5.4 to 7.0 MHz) and separated from the chrominance signal (color) through special Y/C input and output connectors. |
