Luminance / sb → fL
Convert Stilbs to Foot-lamberts
Convert visible-light luminance in candela per projected area. Convert Stilbs (sb) to Foot-lamberts (fL). Find the formula, worked examples, unit definitions, and practical guidance below.
Reverse: Foot-lamberts to Stilbs →
How to convert stilbs to foot-lamberts
Luminance describes directional brightness weighted for human vision. It differs from illuminance on a surface and cannot be converted to lux without geometry.
Use x for the value in sb, b for the intermediate value in cd/m², and y for the result in fL.
fL = sb × 10000 ÷ 3.4262590996353905
Worked examples
10 sb ≈ 29186.350796 fL
Step 1: (10 × 10000) ≈ 100000 cd/m².
Step 2: 100000 ÷ 3.42625909964 ≈ 29186.350796 fL.20 sb ≈ 58372.701592 fL
Step 1: (20 × 10000) ≈ 200000 cd/m².
Step 2: 200000 ÷ 3.42625909964 ≈ 58372.701592 fL.
Results are rounded to 12 significant digits. Converting units does not increase the precision of the original measurement. Very large or small values outside JavaScript’s finite numeric range are rejected.
About Stilbs
Stilbs (sb) measures luminance under the conventions above. The base value in cd/m² is (x × 10000), where x is the numerical value in sb. Factors shown here are rounded for display; calculations use the stored factor.
About Foot-lamberts
Foot-lamberts (fL) measures luminance under the conventions above. The base value in cd/m² is (x × 3.42625909964), where x is the numerical value in fL. Factors shown here are rounded for display; calculations use the stored factor.
Definitions and sources
Carry the same physical assumptions into subsequent physics calculations.
Stilbs to foot-lamberts reference table
| Stilbs (sb) | Foot-lamberts (fL) |
|---|---|
| 1 | 2918.6350796 |
| 5 | 14593.175398 |
| 10 | 29186.350796 |
| 25 | 72965.87699 |
| 50 | 145931.75398 |
| 100 | 291863.50796 |
| 1000 | 2918635.0796 |
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