Candela per square metre

"Nit (unit)" redirects here. For the unit of information entropy, see Nat (information).

The candela per square metre (cd/m²) is the derived SI unit of luminance. The unit is based on the candela, the SI unit of luminous intensity, and the square metre, the SI unit of area. Nit (nt) is a deprecated non-SI name also used for this unit (1 nit = 1 cd/m²).^[1]

Most consumer desktop liquid crystal displays have luminances of 200 to 300 cd/m²;^[2] the sRGB spec for monitors targets 80 cd/m².^[3] HDTVs range from 450 to about 1000 cd/m².

Nit is believed to come from the Latin nitere, to shine.^[4]

Comparison to 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

See also

• Photometry (optics)

SI photometry unitsv · d · e

Quantity	Symbol[nb 1]	SI unit	Symbol	Dimension	Notes
Luminous energy	Qv [nb 2]	lumen second	lm⋅s	T⋅J	units are sometimes called talbots
Luminous flux	Φv [nb 2]	lumen (= cd⋅sr)	lm	J	also called luminous power
Luminous intensity	Iv	candela (= lm/sr)	cd	J [nb 3]	an SI base unit, luminous flux per unit solid angle
Luminance	Lv	candela per square metre	cd/m2	L−2⋅J	units are sometimes called nits
Illuminance	Ev	lux (= lm/m2)	lx	L−2⋅J	used for light incident on a surface
Luminous emittance	Mv	lux (= lm/m2)	lx	L−2⋅J	used for light emitted from a surface
Luminous exposure	Hv	lux second	lx⋅s	L−2⋅T⋅J
Luminous energy density	ωv	lumen second per metre3	lm⋅s⋅m−3	L−3⋅T⋅J
Luminous efficacy	η [nb 2]	lumen per watt	lm/W	M−1⋅L−2⋅T3⋅J	ratio of luminous flux to radiant flux
Luminous efficiency	V			1	also called luminous coefficient
See also: SI · Photometry · Radiometry

1. ^ Standards organizations recommend that photometric quantities be denoted with a suffix "v" (for "visual") to avoid confusion with radiometric or photon quantities.
2. ^ ^{a b c} Alternative symbols sometimes seen: W for luminous energy, P or F for luminous flux, and ρ or K for luminous efficacy.
3. ^ "J" is the recommended symbol for the dimension of luminous intensity in the International System of Units.

References

1. ^ Pierre Buser and Michel Imbert (1992). Vision. MIT Press. p. 53. ISBN 9780262023368. http://books.google.com/books?id=NSZvt8Ld2-8C&pg=PA53&dq=nit+luminance. 
2. ^ "PC Perspective". http://www.pcper.com/article.php?aid=907&type=expert&pid=3. 
3. ^ "IEC 61966-2-1:1999 Multimedia systems and equipment - Colour measurement and management - Part 2-1: Colour management - Default RGB colour space - sRGB". International Electrotechnical Commission. http://webstore.iec.ch/webstore/webstore.nsf/artnum/025408. 
4. ^ R. L. F. Boyd (ed.) (1992). Astronomical Photometry. Springer. p. 9. ISBN 9780792316534. http://books.google.com/books?id=ojzepXhy9DIC&pg=PA9&dq=nitere+nit+luminance. 

External links

• Radiometry vs. Photometry FAQ