Total emission: lumens (lm)
Luminous efficacy of a lamp (quantity of lumens emitted compared to the electric power consumed):
lumens per watt (lm/W)
Illumination received on a surface within the sensitivity of the human eye (400-700 nm):
lux (lx) = lm/m2 (equivalent to W/m2)
Example: Illumination on a desk: 300 lx.