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:

SI photometry quantities
v
t
Quantity		Unit		Dimension	Notes
Name	Symbol^{[nb 1]}	Name	Symbol	Symbol^{[nb 2]}	Notes
Luminous energy	Q_v^{[nb 3]}	lumen second	lm⋅s	T J	The lumen second is sometimes called the talbot.
Luminous flux, luminous power	Φ_v^{[nb 3]}	lumen (= candela steradian)	lm (= cd⋅sr)	J	Luminous energy per unit time
Luminous intensity	I_v	candela (= lumen per steradian)	cd (= lm/sr)	J	Luminous flux per unit solid angle
Luminance	L_v	candela per square metre	cd/m² (= lm/(sr⋅m²))	L⁻²J	Luminous flux per unit solid angle per unit projected source area. The candela per square metre is sometimes called the nit.
Illuminance	E_v	lux (= lumen per square metre)	lx (= lm/m²)	L⁻²J	Luminous flux incident on a surface
Luminous exitance, luminous emittance	M_v	lumen per square metre	lm/m²	L⁻²J	Luminous flux emitted from a surface
Luminous exposure	H_v	lux second	lx⋅s	L⁻²T J	Time-integrated illuminance
Luminous energy density	ω_v	lumen second per cubic metre	lm⋅s/m³	L⁻³T J
Luminous efficacy (of radiation)	K	lumen per watt	lm/W	M⁻¹L⁻²T³J	Ratio of luminous flux to radiant flux
Luminous efficacy (of a source)	η^{[nb 3]}	lumen per watt	lm/W	M⁻¹L⁻²T³J	Ratio of luminous flux to power consumption
Luminous efficiency, luminous coefficient	V			1	Luminous efficacy normalized by the maximum possible efficacy
See also: SI · Photometry · Radiometry

^ 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
^ 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.
^ ^a ^b ^c Alternative symbols sometimes seen: W for luminous energy, P or F for luminous flux, and ρ for luminous efficacy of a source.

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