Quantity |
Symbol |
SI unit |
Abbr. |
Notes |
Luminous energy |
Qv |
lumen second |
lm·s |
units are sometimes called talbots |
Luminous flux |
F |
lumen (= cd·sr) |
lm |
also called luminous power |
Luminous intensity |
Iv |
candela (= lm/sr) |
cd |
an SI base unit |
Luminance |
Lv |
candela per square metre |
cd/m2 |
units are sometimes called "nits" |
Illuminance |
Ev |
lux (= lm/m2) |
lx |
Used for light incident on a surface |
Luminous emittance |
Mv |
lux (= lm/m2) |
lx |
Used for light emitted from a surface |
Luminous efficacy |
|
lumen per watt |
lm/W |
ratio of luminous flux to radiant flux |
See also SI · Photometry · Radiometry |