foot-lambert
Sign in to saveAlso known as footlambert
A foot-lambert or footlambert (fL, sometimes fl or ft-L) is a unit of luminance in United States customary units and some other unit systems. A foot-lambert equals 1/ or 0.3183 candela per square foot, or 3.426 candela per square meter (the corresponding SI unit). The foot-lambert is named after Johann Heinrich Lambert (1728–1777), a Swiss-German mathematician, physicist and astronomer. It is rarely used by electrical and lighting engineers, who prefer the candela per square foot or candela per square meter units.
Wikidata facts
Show 4 more facts
- Wikidata SPARQL query equivalent
- wd:Q5465726 p:P2370/psn:P2370 [wikibase:quantityAmount ?source; wikibase:quantityUnit ?base]. ?item p:P2370/psn:P2370 [wikibase:quantityAmount ?target; wikibase:quantityUnit ?base]. BIND(?source / ?target as ?value)
- unit symbol
- fL
- conversion to SI unit
- 3.4262590996353905269167459616502185942345836205242895980081457842261522902636239909934874631928747639705405275598722719276552
- measured physical quantity
- luminance
Sources (1)
via Wikidata · CC0
~3 min read
Encyclopedic overview
2 sectionsContents
- See also
- References
A foot-lambert or footlambert (fL, sometimes fl or ft-L) is a unit of luminance in United States customary units and some other unit systems. A foot-lambert equals 1/ or 0.3183 candela per square foot, or 3.426 candela per square meter (the corresponding SI unit). The foot-lambert is named after Johann Heinrich Lambert (1728–1777), a Swiss-German mathematician, physicist and astronomer. It is rarely used by electrical and lighting engineers, who prefer the candela per square foot or candela per square meter units.
The luminance of a perfect Lambertian diffuse reflecting surface in foot-lamberts is equal to the incident illuminance in foot-candles. For real diffuse reflectors, the ratio of luminance to illuminance in these units is roughly equal to the reflectance of the surface. Mathematically, L_\mathrm v = E_\mathrm v \times R, where L_\mathrm v is the luminance, in foot-lamberts; E_\mathrm v is the illuminance, in foot-candles; and R is the reflectivity, expressed as a fractional number (for example, a grey card with 18% reflectivity would have
Excerpted from Wikipedia’s “foot-lambert” article, available under the CC BY-SA 4.0 licence.