Luminance / fL → asb
Convert Foot-lamberts to Apostilbs
Convert visible-light luminance in candela per projected area. Convert Foot-lamberts (fL) to Apostilbs (asb). Find the formula, worked examples, unit definitions, and practical guidance below.
Reverse: Apostilbs to Foot-lamberts →
How to convert foot-lamberts to apostilbs
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 fL, b for the intermediate value in cd/m², and y for the result in asb.
asb = fL × 3.4262590996353905 ÷ 0.3183098861837907
Worked examples
10 fL ≈ 107.639104167 asb
Step 1: (10 × 3.42625909964) ≈ 34.2625909964 cd/m².
Step 2: 34.2625909964 ÷ 0.318309886184 ≈ 107.639104167 asb.20 fL ≈ 215.278208334 asb
Step 1: (20 × 3.42625909964) ≈ 68.5251819927 cd/m².
Step 2: 68.5251819927 ÷ 0.318309886184 ≈ 215.278208334 asb.
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 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.
About Apostilbs
Apostilbs (asb) measures luminance under the conventions above. The base value in cd/m² is (x × 0.318309886184), where x is the numerical value in asb. Factors shown here are rounded for display; calculations use the stored factor.
Definitions and sources
Carry the same physical assumptions into subsequent physics calculations.
Foot-lamberts to apostilbs reference table
| Foot-lamberts (fL) | Apostilbs (asb) |
|---|---|
| 1 | 10.7639104167 |
| 5 | 53.8195520835 |
| 10 | 107.639104167 |
| 25 | 269.097760418 |
| 50 | 538.195520835 |
| 100 | 1076.39104167 |
| 1000 | 10763.9104167 |
Browse every luminance conversion →