Illuminance
2-1-055
Illuminance (at a point of a surface)
The quotient of the luminous flux (dF) incident on an infinitesimal element of the surface containing the point under consideration, by the area (dA) of that element.
Symbol: E
Unit: lux (lx)
lumen per square metre (lm/m2)
Reference: C.I.E. (modified)
Note 1: If the luminous flux may be considered uniformly distributed over a finite plane surface of area A, the illuminance on this surface is given by
(Equation)
where F is the total luminous flux incident on the surface.
Note 2: The continued use of the former term Illumination with the meaning above is now deprecated as this use conflicts with the general meaning of the term (2-5-010).
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
