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 (στίλβειν), 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terms such as candle per square inch and candle per square meter were more common.[2] The unit has since largely been replaced by the SI unit: candela per square meter.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]
| cd/m2 (SI unit) ≡ nit ≡ lm/m2/sr |
stilb (sb) (CGS unit) ≡ cd/cm2 |
apostilb (asb) ≡ blondel |
bril | skot (sk) | lambert (L) | foot-lambert (fL) = 1 ⁄ π cd/ft2 | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| 1 cd/m2 | = | 1 | 10−4 | π ≈ 3.142 |
107 π ≈ 3.142×107 |
103 π ≈ 3.142×103 |
10−4 π ≈ 3.142×10−4 |
0.30482 π ≈ 0.2919 | ||
| 1 sb | = | 104 | 1 | 104 π ≈ 3.142×104 |
1011 π ≈ 3.142×1011 |
107 π ≈ 3.142×107 |
π ≈ 3.142 |
30.482 π ≈ 2919 | ||
| 1 asb | = | 1 ⁄ π ≈ 0.3183 |
10−4 ⁄ π ≈ 3.183×10−5 |
1 | 107 | 103 | 10−4 | 0.30482 ≈ 0.09290 | ||
| 1 bril | = | 10−7 ⁄ π ≈ 3.183×10−8 |
10−11 ⁄ π ≈ 3.183×10−12 |
10−7 | 1 | 10−4 | 10−11 | 0.30482×10−7 ≈ 9.290×10−9 | ||
| 1 sk | = | 10−3 ⁄ π ≈ 3.183×10−4 |
10−7 ⁄ π ≈ 3.183×10−8 |
10−3 | 104 | 1 | 10−7 | 0.30482×10−3 ≈ 9.290×10−5 | ||
| 1 L | = | 104 ⁄ π ≈ 3183 |
1 ⁄ π ≈ 0.3183 |
104 | 1011 | 107 | 1 | 0.30482×104 ≈ 929.0 | ||
| 1 fL | = | 1 ⁄ 0.30482 ⁄ π ≈ 3.426 |
1 ⁄ 30.482 ⁄ π ≈ 3.426×10−4 |
1 ⁄ 0.30482 ≈ 10.76 |
107 ⁄ 0.30482 ≈ 1.076×108 |
103 ⁄ 0.30482 ≈ 1.076×104 |
10−4 ⁄ 0.30482 ≈ 1.076×10−3 |
1 | ||
| Quantity | Unit | Dimension [nb 1] |
Notes | ||
|---|---|---|---|---|---|
| Name | Symbol[nb 2] | Name | Symbol | ||
| Luminous energy | Qv[nb 3] | lumen second | lm⋅s | T⋅J | The lumen second is sometimes called the talbot. |
| Luminous flux, luminous power | Φv[nb 3] | lumen (= candela steradian) | 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 (= lm/(sr⋅m2)) | L−2⋅J | 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−2⋅J | Luminous flux incident on a surface |
| Luminous exitance, luminous emittance | Mv | lumen per square metre | lm/m2 | L−2⋅J | Luminous flux emitted from a surface |
| Luminous exposure | Hv | lux second | lx⋅s | L−2⋅T⋅J | Time-integrated illuminance |
| Luminous energy density | ωv | lumen second per cubic metre | lm⋅s/m3 | L−3⋅T⋅J | |
| Luminous efficacy (of radiation) | K | lumen per watt | lm/W | M−1⋅L−2⋅T3⋅J | Ratio of luminous flux to radiant flux |
| Luminous efficacy (of a source) | η[nb 3] | lumen per watt | lm/W | M−1⋅L−2⋅T3⋅J | Ratio of luminous flux to power consumption |
| Luminous efficiency, luminous coefficient | V | 1 | Luminous efficacy normalized by the maximum possible efficacy | ||
| See also: | |||||