Luminance Luminance Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted or reflected from a particular area, and falls within a given solid angle. The SI unit for luminance is candela per square metre (cd/m). A non-SI term for the same unit is the nit. The CGS unit of luminance is the stilb, which is equal to one candela per square centimetre or 10 kcd/m. Luminance is often used to characterize emission or reflection from flat, diffuse surfaces. The luminance
Pre-measure Σ includes "R"). The infimum of the empty set is taken to be formula_6. Pre-measure In mathematics, a pre-measure is a function that is, in some sense, a precursor to a "bona fide" measure on a given space. Indeed, one of the fundamental theorems in measure theory states that a pre-measure can be extended to a measure. Let "R" be a ring of subsets (closed under union and relative complement) of a fixed set "X" and let "μ": "R" → [0, +∞] be a set function. "μ" is called a pre-measure if and, for every countable (or finite) sequence {"A"}