# Stilb (unit)

The stilb (sb) is the CGS unit of luminance for objects that are not self-luminous. It is equal to one candela per square centimeter or 104 nits (candelas per square meter). The name was coined by the French physicist André Blondel around 1920.[1] It comes from the Greek word stilbein meaning "to glitter".

It was in common use in Europe up to World War I. In North America self-explanatory terms such as candle per square inch and candle per square meter were more common.[2] The unit has since largely been replaced by the SI unit: candela per square meter. The current national standard for SI in the United States discourages the use of the stilb.[3]

## Unit conversion

Candela
${\displaystyle \mathrm {1\,{\frac {cd}{m^{2}}}=10^{-4}\,sb} }$
${\displaystyle \mathrm {1\,sb=1\,{\frac {cd}{cm^{2}}}=10^{4}\,{\frac {cd}{m^{2}}}} }$
Nit
${\displaystyle \mathrm {1\,sb=10^{4}\,nit=10^{7}\,millinit} }$
Lambert (L), Apostilb (asb), Blondel, Skot (sk), Bril
${\displaystyle \mathrm {1\,sb=1\pi \,L=10^{3}\pi \,mL=10^{4}\,\pi \,asb=10^{4}\pi \,blondel=10^{7}\pi \,sk=10^{11}\pi \,bril} }$
Footlambert (fL)
${\displaystyle \mathrm {1\,sb\approx 0.3048^{2}\cdot 10^{4}\cdot \pi \,\,fL=2918.6...\,fL} }$

SI photometry quantities
Quantity Unit Dimension Notes
Name Symbol[nb 1] Name Symbol Symbol[nb 2]
Luminous energy Qv[nb 3] lumen second lm⋅s TJ The lumen second is sometimes called the talbot.
Luminous flux, luminous power Φv[nb 3] lumen (= candela steradians) lm (= cd⋅sr) J Luminous energy per unit time
Luminous intensity Iv candela (= lumen per steradian) cd (= lm/sr) J Luminous flux per unit solid angle
Luminance Lv candela per square metre cd/m2 L−2J Luminous flux per unit solid angle per unit projected source area. The candela per square metre is sometimes called the nit.
Illuminance Ev lux (= lumen per square metre) lx (= lm/m2) L−2J Luminous flux incident on a surface
Luminous exitance, luminous emittance Mv lumen per square metre lm/m2 L−2J Luminous flux emitted from a surface
Luminous exposure Hv lux second lx⋅s L−2TJ Time-integrated illuminance
Luminous energy density ωv lumen second per cubic metre lm⋅s/m3 L−3TJ
Luminous efficacy (of radiation) K lumen per watt lm/W M−1L−2T3J Ratio of luminous flux to radiant flux
Luminous efficacy (of a source) η[nb 3] lumen per watt lm/W M−1L−2T3J Ratio of luminous flux to power consumption
Luminous efficiency, luminous coefficient V 1 Luminous efficacy normalized by the maximum possible efficacy