The CGS unit of luminance is the stilb, which is equal to one candela per square centimetre or 10 kcd/m2. Luminance is often used to characterize emission or reflection from flat, diffuse surfaces. Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. The SI unit for luminance is candela per square metre (cd/m2). Luminance is thus an indicator of how bright the surface will appear. It describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle. A non-SI term for the same unit is the "nit". In this case, the solid angle of interest is the solid angle subtended by the eye' s pupil. Luminance is used in the video industry to characterize the brightness of displays. A typical computer display emits between 50 and 300 cd/m2. The sun has luminance of about 1. 6? 109 cd/m2 at noon. The luminance indicates how much luminous power will be perceived by an eye looking at the surface from a particular angle of view.
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