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luminous exitance[′lü·mə·nəs ′ek·səd·əns]
a photometric quantity. The luminous exitance from a point of a surface is the ratio of the luminous flux emitted from an infinitesimal element of surface containing the given point to the area of the element. The unit of luminous exitance in the International System of Units is the lumen per square meter (lm/m2). Radiant exitance, the analogous radiometric quantity, is measured in watts per square meter.