The apostilb is a largely obsolete unit of luminance. The SI unit of luminance is the candela per square metre (cd/m2). In 1942 Parry Moon proposed to rename the apostilb the blondel, after the French physicist André Blondel. The symbol for the apostilb is asb.

The apostilb is defined in terms of another unit of luminance, the stilb (sb): 1 asb = 1/ ⋅ 10−4 sb asb = 1 cd/m2

Applications While now considered obsolete in perimetry, Humphrey visual field analysers still specify the illumination in the system in apostilbs.

Table of SI photometry quantities for reference

See also Other units of luminance:

Lambert (L) Skot (sk) Bril (bril) Nit (nit) Foot-lambert (fL)

References