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
Borel measure for every half-open interval formula_14 is sometimes called "the" Borel measure on formula_10. This measure turns out to be the restriction on the Borel σ-algebra of the Lebesgue measure formula_16, which is a complete measure and is defined on the Lebesgue σ-algebra. The Lebesgue σ-algebra is actually the "completion" of the Borel σ-algebra, which means that it is the smallest σ-algebra which contains all the Borel sets and has a complete measure on it. Also, the Borel measure and the Lebesgue measure coincide on the Borel sets (i.e., formula_17 for every Borel measurable set, where formula_4 is the Borel measure