A CGS unit of luminance. Luminance is the luminous intensity of a surface, measuring the intensity of the light emitted (or reflected) in all directions per unit of area of the surface. One lambert is the luminance of a surface that emits or reflects one lumen per square centimeter. The lambert is a large unit, and practical measurements tend to be in millilamberts (mLa). A geometric calculation shows that a surface area having an intensity of one candela per square meter emits a total light flux of pi lumens per square meter; as a result, one lambert equals 10⁴/pi = 3183.099 candelas per square meter and 1 millilambert equals 3.183 099 candelas per square meter. The lambert honors the German physicist Johann Lambert (1728-1777), who showed that the illuminance of a surface is inversely proportional to the square of the distance from the light source. There has never been agreement on the symbol for the lambert; La is a good choice because it is unlikely to be confused with any other unit symbol