Systems. 2 This means that for an ideal optical system, the luminance at the output is the same as the input luminance.
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3 Mathematical definition edit Parameters for defining the luminance The luminance of a specified point of a light source, in a specified direction, is defined by the derivative Lvd2vddcosdisplaystyle L_mathrm v frac mathrm d 2Phi _mathrm v mathrm. Système international d'unités ) standard for the modern metric system. The unit in the, centimetregramsecond system of units (CGS) (which predated the SI system) is the stilb, which is equal to one candela per square centimetre or 10 kcd/m2. One candela per square metre is equal to: See also edit List edit Table of SI light-related units edit SI photometry quantities Standards organizations recommend that photometric quantities be denoted with a suffix "v" (for "visual to avoid confusion with radiometric or photon quantities. Luminance levels indicate how much luminous power detected by the human eye looking at a particular surface from a particular angle of view. "e-ILV : Luminance meter". The simplest devices measure the luminance in a single direction while imaging luminance meters measure luminance in a way similar to the way a digital camera records color images.
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For real, passive optical systems, the output luminance is at most equal to the input. A typical computer display emits between 50 and 300 cd/m2. 5, Metrology of Optical Components and Systems. The light at the image plane, however, fills a larger solid angle so the luminance comes out to be the same assuming there is no loss at the lens. Archived from the original. As the ray crosses an arbitrary surface S, the luminance is given by Lvd2vdSdScosSdisplaystyle L_mathrm v frac mathrm d 2Phi _mathrm v mathrm d S,mathrm d Omega _Scos theta _S where dS is the infinitesimal area. The image can never be "brighter" than the source.
Health effects edit Further information: Laser safety Retinal damage can occur when the eye is exposed to high luminance. Introduction to Nonimaging Optics, Second Edition. A non-SI term for the same unit is the nit. For other uses, see. Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. Not to be confused with, luma (video), Luminescence, or, illuminance. In this case, the solid angle of interest is the solid angle subtended by the eye's pupil.