Bril (unit)

The bril is an old, non-SI, unit of luminance. The SI unit of luminance is the candela per square metre.

Unit conversions

One bril is equal to:

• $\frac{1}{10^7\pi}$ candela per square metre
• 10⁻⁴ skots
• 10⁻¹¹ lamberts
• 10⁻⁷ apostilbs
• $\frac{1}{10^{11}\pi}$ stilbs (candela per square centimetre)
• about 9.29×10⁻⁹ foot-lamberts

See also

• Photometry (optics)

SI photometry quantities

Quantity		Unit		Dimension	Notes
Name	Symbol[nb 1]	Name	Symbol	Symbol
Luminous energy	Qv [nb 2]	lumen second	lm⋅s	T⋅J [nb 3]	Units are sometimes called talbots.
Luminous flux / luminous power	Φv [nb 2]	lumen (= cd⋅sr)	lm	J [nb 3]	Luminous energy per unit time.
Luminous intensity	Iv	candela (= lm/sr)	cd	J [nb 3]	Luminous power per unit solid angle.
Luminance	Lv	candela per square metre	cd/m^2	L^−2⋅J	Luminous power per unit solid angle per unit projected source area. Units are sometimes called nits.
Illuminance	Ev	lux (= lm/m^2)	lx	L^−2⋅J	Luminous power incident on a surface.
Luminous exitance / luminous emittance	Mv	lux	lx	L^−2⋅J	Luminous power emitted from a surface.
Luminous exposure	Hv	lux second	lx⋅s	L^−2⋅T⋅J
Luminous energy density	ωv	lumen second per cubic metre	lm⋅s⋅m^−3	L^−3⋅T⋅J
Luminous efficacy	η [nb 2]	lumen per watt	lm/W	M^−1⋅L^−2⋅T^3⋅J	Ratio of luminous flux to radiant flux or power consumption, depending on context.
Luminous efficiency / luminous coefficient	V			1
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. For example: USA Standard Letter Symbols for Illuminating Engineering USAS Z7.1-1967, Y10.18-1967
2. Alternative symbols sometimes seen: W for luminous energy, P or F for luminous flux, and ρ or K for luminous efficacy.
3. "J" here is the symbol for the dimension of luminous intensity, not the symbol for the unit joules.