Photometric Units
Photometric Units
SI Units
Quantity
Unit
Luminous flux
lumen lm
Luminous intensity
candela cd
Luminance
cd/m2
Illuminance
lm/m2 lx
Non-SI Units
Luminous Intensity
candlepower = the candela
Luminance
1 stilb = 1 cd/cm
2 = 10,000 cd/m
2
1 apostilb = (1/p) cd/m
2 = 0.3183 cd/m
2
1 lambert = (10,000/p) cd/m
2 = 3183 cd/m
2
1 millilambert = 0.001 lambert = 3.183 cd/m
2
1 footlambert = (1/p) cd/ft
2 = 3.426 cd/m
2
1 candela/ft
2 = 10.76 cd/m
2
1 candela/in.
2 = 1550 cd/m
2
Illuminance
1 footcandle = 1 lm/ft
2 = 10.76 lm/m
2 or lx
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