Apostilb (asb)
The apostilb is (1/π) candela per square metre. Visual-field perimeters (Humphrey) use it for stimulus brightness, often expressed in decibels of attenuation.
Symbol: asb
Quantity: luminance (brightness of a surface or screen)
SI relation: 1 asb = 0.3183098861838 cd/m² (exact)
Derivation: 1 asb = (1/π) cd/m² ≈ 0.3183 cd/m².
Exact: yes, by definition
Typical uses
- Ophthalmic perimetry
- Older European lighting data
Convert apostilbs to other units
| Conversion | 1 asb equals | Reverse |
|---|---|---|
| apostilb to nit | 0.3183098862 cd/m² | nit to apostilb |
| apostilb to foot-lambert | 0.09290304 fL | foot-lambert to apostilb |
| apostilb to candela per square foot | 0.02957195609 cd/ft² | candela per square foot to apostilb |
| apostilb to candela per square inch | 0.0002053608062 cd/in² | candela per square inch to apostilb |
| apostilb to stilb | 0.00003183098862 sb | stilb to apostilb |
| apostilb to lambert | 0.0001 L | lambert to apostilb |
Open the Luminance Converter (Nits, cd/m²) to convert any value between all units.
Sources
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "apostilb".
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Apostilb (asb). Retrieved October 25, 2026, from https://scientificconverters.com/units/apostilb/
IEEE
Scientific Converters, "Apostilb (asb)," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/units/apostilb/