the luminous flux received by an elementary surface divided by the area of this surface
Note 1 to entry: In the SI system of units illuminance is expressed in lux (lx) or lumens per square metre (lm/m2). 1 lux is the illuminance produced on a surface of 1 square metre by a luminous flux of 1 lumen uniformly distributed over that surface. [SOURCE: IEC 60050-723:1997, 723-08-30] |