Lighting a particular area, and falls within a given solid angle. The SI unit for luminance is candela per square metre (cd/m). The CGS unit of luminance is the stilb, which is equal to one candela per square centimetre or 10 kcd/m. The amount of useful light emitted from a source or the luminous flux is measured in lumen (lm). The SI unit of illuminance and luminous emittance, being the luminous power per area, is measured in Lux. It is used in photometry as a measure of the intensity, as perceived by the human eye, of light that hits or passes
Complete measure Complete measure In mathematics, a complete measure (or, more precisely, a complete measure space) is a measure space in which every subset of every null set is measurable (having measure zero). More formally, a measure space ("X", Σ, "μ") is complete if and only if The need to consider questions of completeness can be illustrated by considering the problem of product spaces. Suppose that we have already constructed Lebesgue measure on the real line: denote this measure space by (R, "B", "λ"). We now wish to construct some two-dimensional Lebesgue measure "λ" on the plane R as a product measure.