Lux (lx)
Metric unit of measurement for the illumination (E) on a surface. (See footcandle for English unit.) One lux is the illumination on a surface one meter from and perpendicular to a uniform point source of one candela. The formula for lux is:

where CD is the candlepower, A is the angle of incidence of the light beam, and D is the distance of the surface from the light source.