Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction.
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The unit of luminous intensity, candela, is realized by using an absolute radiometer.
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This article is about the unit of luminous intensity.
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Luminous intensity is the perceived power per unit solid angle.
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In 1881, Jules Violle proposed the Violle as a unit of luminous intensity, and it was notable as the first unit of light intensity that did not depend on the properties of a particular lamp.
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Luminous intensity should not be confused with another photometric unit, luminous flux, which is the total perceived power emitted in all directions.