| Candela per square metre | |
|---|---|
| Unit system | SI |
| Unit of | luminance |
| Symbol | cd/m |
| In SI base units: | cd·m |
The candela per square metre (symbol: cd/m) 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 non-SI name also used for this unit (1 nt = 1 cd/m). 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/m. Typically, monitors calibrated for SDR broadcast or studio color grading should have a brightness of 100 cd/m. Most consumer desktop liquid crystal displays have luminances of 200 to 300 cd/m. HDR displays range from around 400 to 2500 cd/m.
Comparison with other units of luminance
One candela per square metre is equal to:
- 10 stilbs (the CGS unit of luminance)
- π×10 lamberts
- π apostilbs
- 0.292 foot-lamberts
- π×10 skots
- π×10 brils
- 1 nit
| cd/m (SI unit) ≡ nit ≡ lm/m/sr |
stilb (sb) (CGS unit) ≡ cd/cm |
apostilb (asb) ≡ blondel |
bril | skot (sk) | lambert (L) | foot-lambert (fL) = 1 ⁄ π cd/ft | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| 1 cd/m | = | 1 | 10 | π ≈ 3.142 |
10 π ≈ 3.142×10 |
10 π ≈ 3.142×10 |
10 π ≈ 3.142×10 |
0.3048 π ≈ 0.2919 | ||
| 1 sb | = | 10 | 1 | 10 π ≈ 3.142×10 |
10 π ≈ 3.142×10 |
10 π ≈ 3.142×10 |
π ≈ 3.142 |
30.48 π ≈ 2919 | ||
| 1 asb | = | 1 ⁄ π ≈ 0.3183 |
10 ⁄ π ≈ 3.183×10 |
1 | 10 | 10 | 10 | 0.3048 ≈ 0.09290 | ||
| 1 bril | = | 10 ⁄ π ≈ 3.183×10 |
10 ⁄ π ≈ 3.183×10 |
10 | 1 | 10 | 10 | 0.3048×10 ≈ 9.290×10 | ||
| 1 sk | = | 10 ⁄ π ≈ 3.183×10 |
10 ⁄ π ≈ 3.183×10 |
10 | 10 | 1 | 10 | 0.3048×10 ≈ 9.290×10 | ||
| 1 L | = | 10 ⁄ π ≈ 3183 |
1 ⁄ π ≈ 0.3183 |
10 | 10 | 10 | 1 | 0.3048×10 ≈ 929.0 | ||
| 1 fL | = | 1 ⁄ 0.3048 ⁄ π ≈ 3.426 |
1 ⁄ 30.48 ⁄ π ≈ 3.426×10 |
1 ⁄ 0.3048 ≈ 10.76 |
10 ⁄ 0.3048 ≈ 1.076×10 |
10 ⁄ 0.3048 ≈ 1.076×10 |
10 ⁄ 0.3048 ≈ 1.076×10 |
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/m (= lm/(sr⋅m)) | L⋅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/m) | L⋅J | Luminous flux incident on a surface |
| Luminous exitance, luminous emittance | Mv | lumen per square metre | lm/m | L⋅J | Luminous flux emitted from a surface |
| Luminous exposure | Hv | lux second | lx⋅s | L⋅T⋅J | Time-integrated illuminance |
| Luminous energy density | ωv | lumen second per cubic metre | lm⋅s/m | L⋅T⋅J | |
| Luminous efficacy (of radiation) | K | lumen per watt | lm/W | M⋅L⋅T⋅J | Ratio of luminous flux to radiant flux |
| Luminous efficacy (of a source) | η | lumen per watt | lm/W | M⋅L⋅T⋅J | Ratio of luminous flux to power consumption |
| Luminous efficiency, luminous coefficient | V | 1 | Luminous efficacy normalized by the maximum possible efficacy | ||
| See also: | |||||
- The symbols in this column denote dimensions; "L", "T" and "J" are for length, time and luminous intensity respectively, not the symbols for the units litre, tesla and joule.
- Standards organizations recommend that photometric quantities be denoted with a subscript "v" (for "visual") to avoid confusion with radiometric or photon quantities. For example: USA Standard Letter Symbols for Illuminating Engineering USAS Z7.1-1967, Y10.18-1967
- ^ Alternative symbols sometimes seen: W for luminous energy, P or F for luminous flux, and ρ for luminous efficacy of a source.
References
- Buser, Pierre; Imbert, Michel (1992). Vision. MIT Press. p. 53. ISBN 978-0-262-02336-8.
nit luminance.
- Boyd, RLF, ed. (1992). Astronomical Photometry. Springer. p. 9. ISBN 978-0-7923-1653-4.
- "Multimedia systems and equipment – Colour measurement and management – Part 2-1: Colour management – Default RGB colour space – sRGB". International Electrotechnical Commission. 1999. IEC 61966-2-1.
- "ITU-R BT.2035-7" (PDF). A reference viewing environment for evaluation of HDTV program material or completed programmes. 2013-08-13. Archived (PDF) from the original on 2022-12-20. Retrieved 2022-12-20.
- Hung, Jonathan (May 3, 2010). "Acer Ferrari One 200 Review – More than a Netbook". PC Perspective. Retrieved 2018-01-21.
- Cohen, Steven. "What is HDR? High dynamic range TVs and formats, explained". Business Insider. Retrieved 2024-05-08.
External links
- IEC 61966-2-1:1999 Multimedia systems and equipment – Colour measurement and management – Part 2-1: Colour management – Default RGB colour space – sRGB
- IEC International System of Units zone