Convert Apostilbs to Foot-lamberts
Convert Apostilbs (asb) to Foot-lamberts (fL) instantly and accurately.
Conversion Formula
fL = asb × 0.09290304
About Apostilbs
The apostilb (asb) equals 1/π cd/m² ≈ 0.3183 cd/m², defined as the luminance of a perfectly diffuse Lambertian surface with an exitance of 1 lm/m². Introduced by the CIE in 1940 and used in European photometry standards and retinal illuminance calculations. 1 asb = 1/π cd/m² ≈ 0.3183 cd/m².
About Foot-lamberts
The foot-lambert (fL) equals 1/(π×0.09290304) cd/m² ≈ 3.426 cd/m², the luminance of a perfect diffuse surface emitting 1 lumen per square foot. The SMPTE standard for cinema screen luminance is 14 fL (≈48 cd/m²); home projectors are rated 10-35 fL. Still standard in US cinema and theatre engineering. 1 fL = 1/(π×ft²) cd/m².
Quick Reference Table
| Apostilbs (asb) | Foot-lamberts (fL) |
|---|---|
| 1 asb | 0.092903 fL |
| 2 asb | 0.185806 fL |
| 5 asb | 0.464515 fL |
| 10 asb | 0.92903 fL |
| 25 asb | 2.32258 fL |
| 50 asb | 4.64515 fL |
| 100 asb | 9.2903 fL |