Foot-Lambert calculator

is a unit of luminance (the intensity of light emitted from a surface). It is the luminance of a perfectly diffusing surface emitting or reflecting 1 lumen per square foot. This unit is used in the US and Canada, and worldwide in the cinema business.
     To calculate from screen dimensions, click here

Luminance conversion

Nit
1911 cd/m2
Candela per square meter
1911 cd/m2
Candela per square foot
177.5 cd/sq.ft.
Stilb (CGS)
0.1911 Stilb
Apostilb (blondel)
608.29 Apostilb
Lambert
0.060829 Lambert
Foot-Lambert
558 ftL
Exposure Value
13.9 EV

Screen luminance: EV13.9

-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
starlight to dim ambient lightmoon eclipse to night home interiorneon lights to landscape after sunsetbright light to weak sunbright daylight to direct sunlight

Explanation

A foot-lambert or footlambert (ftL, sometimes fl or ft-L) is a unit of luminance. For screens that are projected upon (like cinema, home cinema), it quantifies how much light is reflected (to the center of the room). This depends on the amount of light produced (lumens), the size of the screen and the screen gain.

Examples

Cinema: 32000 lumen on 23x10m screen

References

Foot-lambert
Lambert
Nit
Screen gain
Stilb