Candela per square metre
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The candela per square metre (symbol: cd/m2) is the unit of luminance in the International System of Units (SI). The unit is based on the candela, the SI unit of luminous intensity, and the square metre, the SI unit of area.
The nit (symbol: nt) is a deprecated non-SI name also used for this unit (1 nt = 1 cd/m2). The term nit is believed to come from the Latin word nitēre, "to shine".
As a measure of light emitted per unit area, this unit is frequently used to specify the brightness of a display device. The sRGB spec for monitors targets 80 cd/m2. Typically, monitors calibrated for SDR broadcast or studio color grading should have a brightness of 100 cd/m2. Most consumer desktop liquid crystal displays have luminances of 200 to 300 cd/m2. HDR displays range from around 400 to 2500 cd/m2.
Comparison with other units of luminance
One candela per square metre is equal to:
- 10−4 stilbs (the CGS unit of luminance)
- π × 10−4 lamberts
- π apostilbs
- 0.292 foot-lamberts
- π × 103 skots
- π × 107 brils
- 1 nit
| vte | 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 ≈ 2,919 | |
| 1 asb | = | 1 ⁄ π ≈ 0.3183 | 10−4 ⁄ π ≈ 3.183×10−5 | 1 | 107 | 103 | 10−4 | 0.30482 ≈ 0.0929 | |
| 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 ≈ 9.29×10−9 | |
| 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 ≈ 9.29×10−5 | |
| 1 L | = | 104 ⁄ π ≈ 3,183 | 1 ⁄ π ≈ 0.3183 | 104 | 1011 | 107 | 1 | 0.30482×104 ≈ 929 | |
| 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 |
See also
| Quantity | Unit | Dimension | Notes | ||
|---|---|---|---|---|---|
| Name | Symbol | Name | Symbol | ||
| Luminous energy | Qv | lumen second | lm⋅s | T⋅J | The lumen second is sometimes called the talbot. |
| Luminous flux, luminous power | Φv | 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 | 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: SIPhotometryRadiometry |