Template:SI photon units/doc

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This template displays a table of SI photon units for usage in articles about physics or radiometry. It may also serve as a navigation box at the end of corresponding articles.

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SI photon units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^{[nb 1]}	Name	Symbol	Dimension	Notes
photon energy	$n$			1	count of photons $n$ with energy $Q p = h c / λ$ .^{[nb 2]}
photon flux	$Φ q$	count per second	s⁻¹	T⁻¹	photons per unit time, $d n /d t$ with $n$ = photon number. also called photon power
photon intensity	$I$	count per steradian per second	sr⁻¹⋅s⁻¹	T⁻¹	$d n /d ω$
photon radiance	$L q$	count per square metre per steradian per second	m⁻²⋅sr⁻¹⋅s⁻¹	L⁻²‍T⁻¹	$d 2 n /(d A cos(θ) d ω)$
photon irradiance	$E q$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
photon exitance	$M$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
See also: Photon counting SI Radiometry Photometry

^ Standards organizations recommend that photon quantities be denoted with a suffix "q" (for "quantum") to avoid confusion with radiometric and photometric quantities.
^ The energy of a single photon at wavelength $λ$ is $Q p = hc / λ$ with $h$ = Planck constant and $c$ = velocity of light.

Table 1. SI photon units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^{[nb 1]}	Name	Symbol	Dimension	Notes
photon energy	$n$			1	count of photons $n$ with energy $Q p = h c / λ$ .^{[nb 2]}
photon flux	$Φ q$	count per second	s⁻¹	T⁻¹	photons per unit time, $d n /d t$ with $n$ = photon number. also called photon power
photon intensity	$I$	count per steradian per second	sr⁻¹⋅s⁻¹	T⁻¹	$d n /d ω$
photon radiance	$L q$	count per square metre per steradian per second	m⁻²⋅sr⁻¹⋅s⁻¹	L⁻²‍T⁻¹	$d 2 n /(d A cos(θ) d ω)$
photon irradiance	$E q$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
photon exitance	$M$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
See also: Photon counting SI Radiometry Photometry

^ Standards organizations recommend that photon quantities be denoted with a suffix "q" (for "quantum") to avoid confusion with radiometric and photometric quantities.
^ The energy of a single photon at wavelength $λ$ is $Q p = hc / λ$ with $h$ = Planck constant and $c$ = velocity of light.

Table 1. SI photon units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^{[nb 1]}	Name	Symbol	Dimension	Notes
photon energy	$n$			1	count of photons $n$ with energy $Q p = h c / λ$ .^{[nb 2]}
photon flux	$Φ q$	count per second	s⁻¹	T⁻¹	photons per unit time, $d n /d t$ with $n$ = photon number. also called photon power
photon intensity	$I$	count per steradian per second	sr⁻¹⋅s⁻¹	T⁻¹	$d n /d ω$
photon radiance	$L q$	count per square metre per steradian per second	m⁻²⋅sr⁻¹⋅s⁻¹	L⁻²‍T⁻¹	$d 2 n /(d A cos(θ) d ω)$
photon irradiance	$E q$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
photon exitance	$M$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
See also: Photon counting SI Radiometry (Compare)\| Photometry\|(Compare)

^ Standards organizations recommend that photon quantities be denoted with a suffix "q" (for "quantum") to avoid confusion with radiometric and photometric quantities.
^ The energy of a single photon at wavelength $λ$ is $Q p = hc / λ$ with $h$ = Planck constant and $c$ = velocity of light.

SI photon units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^{[nb 1]}	Name	Symbol	Dimension	Notes
photon energy	$n$			1	count of photons $n$ with energy $Q p = h c / λ$ .^{[nb 2]}
photon flux	$Φ q$	count per second	s⁻¹	T⁻¹	photons per unit time, $d n /d t$ with $n$ = photon number. also called photon power
photon intensity	$I$	count per steradian per second	sr⁻¹⋅s⁻¹	T⁻¹	$d n /d ω$
photon radiance	$L q$	count per square metre per steradian per second	m⁻²⋅sr⁻¹⋅s⁻¹	L⁻²‍T⁻¹	$d 2 n /(d A cos(θ) d ω)$
photon irradiance	$E q$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
photon exitance	$M$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
See also: Photon counting SI Radiometry (Compare)\| Photometry\|(Compare)

^ Standards organizations recommend that photon quantities be denoted with a suffix "q" (for "quantum") to avoid confusion with radiometric and photometric quantities.
^ The energy of a single photon at wavelength $λ$ is $Q p = hc / λ$ with $h$ = Planck constant and $c$ = velocity of light.

Table 1. SI photon units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^[1]	Name	Symbol	Dimension	Notes
photon energy	$n$			1	count of photons $n$ with energy $Q p = h c / λ$ .^[2]
photon flux	$Φ q$	count per second	s⁻¹	T⁻¹	photons per unit time, $d n /d t$ with $n$ = photon number. also called photon power
photon intensity	$I$	count per steradian per second	sr⁻¹⋅s⁻¹	T⁻¹	$d n /d ω$
photon radiance	$L q$	count per square metre per steradian per second	m⁻²⋅sr⁻¹⋅s⁻¹	L⁻²‍T⁻¹	$d 2 n /(d A cos(θ) d ω)$
photon irradiance	$E q$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
photon exitance	$M$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
See also: Photon counting SI Radiometry (Compare)\| Photometry\|(Compare)

Table 1. SI photon units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^[1]	Name	Symbol	Dimension	Notes
photon energy	$n$			1	count of photons $n$ with energy $Q p = h c / λ$ .^[2]
photon flux	$Φ q$	count per second	s⁻¹	T⁻¹	photons per unit time, $d n /d t$ with $n$ = photon number. also called photon power
photon intensity	$I$	count per steradian per second	sr⁻¹⋅s⁻¹	T⁻¹	$d n /d ω$
photon radiance	$L q$	count per square metre per steradian per second	m⁻²⋅sr⁻¹⋅s⁻¹	L⁻²‍T⁻¹	$d 2 n /(d A cos(θ) d ω)$
photon irradiance	$E q$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
photon exitance	$M$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
See also: Photon counting SI Radiometry Photometry

SI photon units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^[1]	Name	Symbol	Dimension	Notes
photon energy	$n$			1	count of photons $n$ with energy $Q p = h c / λ$ .^[2]
photon flux	$Φ q$	count per second	s⁻¹	T⁻¹	photons per unit time, $d n /d t$ with $n$ = photon number. also called photon power
photon intensity	$I$	count per steradian per second	sr⁻¹⋅s⁻¹	T⁻¹	$d n /d ω$
photon radiance	$L q$	count per square metre per steradian per second	m⁻²⋅sr⁻¹⋅s⁻¹	L⁻²‍T⁻¹	$d 2 n /(d A cos(θ) d ω)$
photon irradiance	$E q$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
photon exitance	$M$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
See also: Photon counting SI Radiometry (Compare)\| Photometry\|(Compare)

Table 1. SI photon units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^{[Note 1]}	Name	Symbol	Dimension	Notes
photon energy	$n$			1	count of photons $n$ with energy $Q p = h c / λ$ .^{[Note 2]}
photon flux	$Φ q$	count per second	s⁻¹	T⁻¹	photons per unit time, $d n /d t$ with $n$ = photon number. also called photon power
photon intensity	$I$	count per steradian per second	sr⁻¹⋅s⁻¹	T⁻¹	$d n /d ω$
photon radiance	$L q$	count per square metre per steradian per second	m⁻²⋅sr⁻¹⋅s⁻¹	L⁻²‍T⁻¹	$d 2 n /(d A cos(θ) d ω)$
photon irradiance	$E q$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
photon exitance	$M$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
See also: Photon counting SI Radiometry (Compare)\| Photometry\|(Compare)

SI photon units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^{[notes 1]}	Name	Symbol	Dimension	Notes
photon energy	$n$			1	count of photons $n$ with energy $Q p = h c / λ$ .^{[notes 2]}
photon flux	$Φ q$	count per second	s⁻¹	T⁻¹	photons per unit time, $d n /d t$ with $n$ = photon number. also called photon power
photon intensity	$I$	count per steradian per second	sr⁻¹⋅s⁻¹	T⁻¹	$d n /d ω$
photon radiance	$L q$	count per square metre per steradian per second	m⁻²⋅sr⁻¹⋅s⁻¹	L⁻²‍T⁻¹	$d 2 n /(d A cos(θ) d ω)$
photon irradiance	$E q$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
photon exitance	$M$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
See also: Photon counting SI Radiometry Photometry

SI photon units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^{[Note 1]}	Name	Symbol	Dimension	Notes
photon energy	$n$			1	count of photons $n$ with energy $Q p = h c / λ$ .^{[Note 2]}
photon flux	$Φ q$	count per second	s⁻¹	T⁻¹	photons per unit time, $d n /d t$ with $n$ = photon number. also called photon power
photon intensity	$I$	count per steradian per second	sr⁻¹⋅s⁻¹	T⁻¹	$d n /d ω$
photon radiance	$L q$	count per square metre per steradian per second	m⁻²⋅sr⁻¹⋅s⁻¹	L⁻²‍T⁻¹	$d 2 n /(d A cos(θ) d ω)$
photon irradiance	$E q$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
photon exitance	$M$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
See also: Photon counting SI Radiometry (Compare)\| Photometry\|(Compare)

</syntaxhighlight>

Combining the tables in a single article (individually grouped footnotes in group "nb"):

Table 1. SI photometry quantities
v
t
e
Quantity		Unit		Dimension ^{[nb 1]}	Notes
Name	Symbol^{[nb 2]}	Name	Symbol	Dimension ^{[nb 1]}	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⁻²⋅J	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⁻²⋅J	Luminous flux incident on a surface
Luminous exitance, luminous emittance	$M v$	lumen per square metre	lm/m²	L⁻²⋅J	Luminous flux emitted from a surface
Luminous exposure	$H v$	lux second	lx⋅s	L⁻²⋅T⋅J	Time-integrated illuminance
Luminous energy density	$ω v$	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)	$η$ ^{[nb 3]}	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: SI Photometry Radiometry\|(Compare)

^ 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
^ ^3.0 ^3.1 ^3.2 Alternative symbols sometimes seen: $W$ for luminous energy, $P$ or $F$ for luminous flux, and $ρ$ for luminous efficacy of a source.

Table 2. SI radiometry units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^{[nb 1]}	Name	Symbol	Dimension	Notes
Radiant energy	$Q e$ ^{[nb 2]}	joule	J	M⋅L²⋅T⁻²	Energy of electromagnetic radiation.
Radiant energy density	$w e$	joule per cubic metre	J/m³	M⋅L⁻¹⋅T⁻²	Radiant energy per unit volume.
Radiant flux	$Φ e$ ^{[nb 2]}	watt	W = J/s	M⋅L²⋅T⁻³	Radiant energy emitted, reflected, transmitted or received, per unit time. This is sometimes also called "radiant power", and called luminosity in Astronomy.
Spectral flux	$Φ e, ν$ ^{[nb 3]}	watt per hertz	W/Hz	M⋅L²⋅T⁻²	Radiant flux per unit frequency or wavelength. The latter is commonly measured in W⋅nm⁻¹.
Spectral flux	$Φ e, λ$ ^{[nb 4]}	watt per metre	W/m	M⋅L⋅T⁻³
Radiant intensity	$I e,Ω$ ^{[nb 5]}	watt per steradian	W/sr	M⋅L²⋅T⁻³	Radiant flux emitted, reflected, transmitted or received, per unit solid angle. This is a directional quantity.
Spectral intensity	$I e,Ω, ν$ ^{[nb 3]}	watt per steradian per hertz	W⋅sr⁻¹⋅Hz⁻¹	M⋅L²⋅T⁻²	Radiant intensity per unit frequency or wavelength. The latter is commonly measured in W⋅sr⁻¹⋅nm⁻¹. This is a directional quantity.
Spectral intensity	$I e,Ω, λ$ ^{[nb 4]}	watt per steradian per metre	W⋅sr⁻¹⋅m⁻¹	M⋅L⋅T⁻³
Radiance	$L e,Ω$ ^{[nb 5]}	watt per steradian per square metre	W⋅sr⁻¹⋅m⁻²	M⋅T⁻³	Radiant flux emitted, reflected, transmitted or received by a surface, per unit solid angle per unit projected area. This is a directional quantity. This is sometimes also confusingly called "intensity".
Spectral radiance Specific intensity	$L e,Ω, ν$ ^{[nb 3]}	watt per steradian per square metre per hertz	W⋅sr⁻¹⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Radiance of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅sr⁻¹⋅m⁻²⋅nm⁻¹. This is a directional quantity. This is sometimes also confusingly called "spectral intensity".
Spectral radiance Specific intensity	$L e,Ω, λ$ ^{[nb 4]}	watt per steradian per square metre, per metre	W⋅sr⁻¹⋅m⁻³	M⋅L⁻¹⋅T⁻³
Irradiance Flux density	$E e$ ^{[nb 2]}	watt per square metre	W/m²	M⋅T⁻³	Radiant flux received by a surface per unit area. This is sometimes also confusingly called "intensity".
Spectral irradiance Spectral flux density	$E e, ν$ ^{[nb 3]}	watt per square metre per hertz	W⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Irradiance of a surface per unit frequency or wavelength. This is sometimes also confusingly called "spectral intensity". Non-SI units of spectral flux density include jansky (1 Jy = 10⁻²⁶ W⋅m⁻²⋅Hz⁻¹) and solar flux unit (1 sfu = 10⁻²² W⋅m⁻²⋅Hz⁻¹ = 10⁴ Jy).
Spectral irradiance Spectral flux density	$E e, λ$ ^{[nb 4]}	watt per square metre, per metre	W/m³	M⋅L⁻¹⋅T⁻³
Radiosity	$J e$ ^{[nb 2]}	watt per square metre	W/m²	M⋅T⁻³	Radiant flux leaving (emitted, reflected and transmitted by) a surface per unit area. This is sometimes also confusingly called "intensity".
Spectral radiosity	$J e, ν$ ^{[nb 3]}	watt per square metre per hertz	W⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Radiosity of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m⁻²⋅nm⁻¹. This is sometimes also confusingly called "spectral intensity".
Spectral radiosity	$J e, λ$ ^{[nb 4]}	watt per square metre, per metre	W/m³	M⋅L⁻¹⋅T⁻³
Radiant exitance	$M e$ ^{[nb 2]}	watt per square metre	W/m²	M⋅T⁻³	Radiant flux emitted by a surface per unit area. This is the emitted component of radiosity. "Radiant emittance" is an old term for this quantity. This is sometimes also confusingly called "intensity".
Spectral exitance	$M e, ν$ ^{[nb 3]}	watt per square metre per hertz	W⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Radiant exitance of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m⁻²⋅nm⁻¹. "Spectral emittance" is an old term for this quantity. This is sometimes also confusingly called "spectral intensity".
Spectral exitance	$M e, λ$ ^{[nb 4]}	watt per square metre, per metre	W/m³	M⋅L⁻¹⋅T⁻³
Radiant exposure	$H e$	joule per square metre	J/m²	M⋅T⁻²	Radiant energy received by a surface per unit area, or equivalently irradiance of a surface integrated over time of irradiation. This is sometimes also called "radiant fluence".
Spectral exposure	$H e, ν$ ^{[nb 3]}	joule per square metre per hertz	J⋅m⁻²⋅Hz⁻¹	M⋅T⁻¹	Radiant exposure of a surface per unit frequency or wavelength. The latter is commonly measured in J⋅m⁻²⋅nm⁻¹. This is sometimes also called "spectral fluence".
Spectral exposure	$H e, λ$ ^{[nb 4]}	joule per square metre, per metre	J/m³	M⋅L⁻¹⋅T⁻²
See also: SI Radiometry Photometry\|(Compare)

^ Standards organizations recommend that radiometric quantities should be denoted with suffix "e" (for "energetic") to avoid confusion with photometric or photon quantities.
^ ^2.0 ^2.1 ^2.2 ^2.3 ^2.4 Alternative symbols sometimes seen: $W$ or $E$ for radiant energy, $P$ or $F$ for radiant flux, $I$ for irradiance, $W$ for radiant exitance.
^ ^3.0 ^3.1 ^3.2 ^3.3 ^3.4 ^3.5 ^3.6 Spectral quantities given per unit frequency are denoted with suffix "ν" (Greek letter nu, not to be confused with a letter "v", indicating a photometric quantity.)
^ ^4.0 ^4.1 ^4.2 ^4.3 ^4.4 ^4.5 ^4.6 Spectral quantities given per unit wavelength are denoted with suffix "λ".
^ ^5.0 ^5.1 Directional quantities are denoted with suffix "Ω".

Table 3. SI photon units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^{[nb 1]}	Name	Symbol	Dimension	Notes
photon energy	$n$			1	count of photons $n$ with energy $Q p = h c / λ$ .^{[nb 2]}
photon flux	$Φ q$	count per second	s⁻¹	T⁻¹	photons per unit time, $d n /d t$ with $n$ = photon number. also called photon power
photon intensity	$I$	count per steradian per second	sr⁻¹⋅s⁻¹	T⁻¹	$d n /d ω$
photon radiance	$L q$	count per square metre per steradian per second	m⁻²⋅sr⁻¹⋅s⁻¹	L⁻²‍T⁻¹	$d 2 n /(d A cos(θ) d ω)$
photon irradiance	$E q$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
photon exitance	$M$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
See also: Photon counting SI Radiometry (Compare)\| Photometry\|(Compare)

^ Standards organizations recommend that photon quantities be denoted with a suffix "q" (for "quantum") to avoid confusion with radiometric and photometric quantities.
^ The energy of a single photon at wavelength $λ$ is $Q p = hc / λ$ with $h$ = Planck constant and $c$ = velocity of light.

</syntaxhighlight>

Combining the tables in a single article (individual footnotes in separately named groups, f.e. "T1", "T2", and "T3"):

Table 1. SI photometry quantities
v
t
e
Quantity		Unit		Dimension ^{[T1 1]}	Notes
Name	Symbol^{[T1 2]}	Name	Symbol	Dimension ^{[T1 1]}	Notes
Luminous energy	$Q v$ ^{[T1 3]}	lumen second	lm⋅s	T⋅J	The lumen second is sometimes called the talbot.
Luminous flux, luminous power	$Φ v$ ^{[T1 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⁻²⋅J	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⁻²⋅J	Luminous flux incident on a surface
Luminous exitance, luminous emittance	$M v$	lumen per square metre	lm/m²	L⁻²⋅J	Luminous flux emitted from a surface
Luminous exposure	$H v$	lux second	lx⋅s	L⁻²⋅T⋅J	Time-integrated illuminance
Luminous energy density	$ω v$	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)	$η$ ^{[T1 3]}	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: SI Photometry Radiometry\|(Compare)

^ 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
^ ^3.0 ^3.1 ^3.2 Alternative symbols sometimes seen: $W$ for luminous energy, $P$ or $F$ for luminous flux, and $ρ$ for luminous efficacy of a source.

Table 2. SI radiometry units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^{[T2 1]}	Name	Symbol	Dimension	Notes
Radiant energy	$Q e$ ^{[T2 2]}	joule	J	M⋅L²⋅T⁻²	Energy of electromagnetic radiation.
Radiant energy density	$w e$	joule per cubic metre	J/m³	M⋅L⁻¹⋅T⁻²	Radiant energy per unit volume.
Radiant flux	$Φ e$ ^{[T2 2]}	watt	W = J/s	M⋅L²⋅T⁻³	Radiant energy emitted, reflected, transmitted or received, per unit time. This is sometimes also called "radiant power", and called luminosity in Astronomy.
Spectral flux	$Φ e, ν$ ^{[T2 3]}	watt per hertz	W/Hz	M⋅L²⋅T⁻²	Radiant flux per unit frequency or wavelength. The latter is commonly measured in W⋅nm⁻¹.
Spectral flux	$Φ e, λ$ ^{[T2 4]}	watt per metre	W/m	M⋅L⋅T⁻³
Radiant intensity	$I e,Ω$ ^{[T2 5]}	watt per steradian	W/sr	M⋅L²⋅T⁻³	Radiant flux emitted, reflected, transmitted or received, per unit solid angle. This is a directional quantity.
Spectral intensity	$I e,Ω, ν$ ^{[T2 3]}	watt per steradian per hertz	W⋅sr⁻¹⋅Hz⁻¹	M⋅L²⋅T⁻²	Radiant intensity per unit frequency or wavelength. The latter is commonly measured in W⋅sr⁻¹⋅nm⁻¹. This is a directional quantity.
Spectral intensity	$I e,Ω, λ$ ^{[T2 4]}	watt per steradian per metre	W⋅sr⁻¹⋅m⁻¹	M⋅L⋅T⁻³
Radiance	$L e,Ω$ ^{[T2 5]}	watt per steradian per square metre	W⋅sr⁻¹⋅m⁻²	M⋅T⁻³	Radiant flux emitted, reflected, transmitted or received by a surface, per unit solid angle per unit projected area. This is a directional quantity. This is sometimes also confusingly called "intensity".
Spectral radiance Specific intensity	$L e,Ω, ν$ ^{[T2 3]}	watt per steradian per square metre per hertz	W⋅sr⁻¹⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Radiance of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅sr⁻¹⋅m⁻²⋅nm⁻¹. This is a directional quantity. This is sometimes also confusingly called "spectral intensity".
Spectral radiance Specific intensity	$L e,Ω, λ$ ^{[T2 4]}	watt per steradian per square metre, per metre	W⋅sr⁻¹⋅m⁻³	M⋅L⁻¹⋅T⁻³
Irradiance Flux density	$E e$ ^{[T2 2]}	watt per square metre	W/m²	M⋅T⁻³	Radiant flux received by a surface per unit area. This is sometimes also confusingly called "intensity".
Spectral irradiance Spectral flux density	$E e, ν$ ^{[T2 3]}	watt per square metre per hertz	W⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Irradiance of a surface per unit frequency or wavelength. This is sometimes also confusingly called "spectral intensity". Non-SI units of spectral flux density include jansky (1 Jy = 10⁻²⁶ W⋅m⁻²⋅Hz⁻¹) and solar flux unit (1 sfu = 10⁻²² W⋅m⁻²⋅Hz⁻¹ = 10⁴ Jy).
Spectral irradiance Spectral flux density	$E e, λ$ ^{[T2 4]}	watt per square metre, per metre	W/m³	M⋅L⁻¹⋅T⁻³
Radiosity	$J e$ ^{[T2 2]}	watt per square metre	W/m²	M⋅T⁻³	Radiant flux leaving (emitted, reflected and transmitted by) a surface per unit area. This is sometimes also confusingly called "intensity".
Spectral radiosity	$J e, ν$ ^{[T2 3]}	watt per square metre per hertz	W⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Radiosity of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m⁻²⋅nm⁻¹. This is sometimes also confusingly called "spectral intensity".
Spectral radiosity	$J e, λ$ ^{[T2 4]}	watt per square metre, per metre	W/m³	M⋅L⁻¹⋅T⁻³
Radiant exitance	$M e$ ^{[T2 2]}	watt per square metre	W/m²	M⋅T⁻³	Radiant flux emitted by a surface per unit area. This is the emitted component of radiosity. "Radiant emittance" is an old term for this quantity. This is sometimes also confusingly called "intensity".
Spectral exitance	$M e, ν$ ^{[T2 3]}	watt per square metre per hertz	W⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Radiant exitance of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m⁻²⋅nm⁻¹. "Spectral emittance" is an old term for this quantity. This is sometimes also confusingly called "spectral intensity".
Spectral exitance	$M e, λ$ ^{[T2 4]}	watt per square metre, per metre	W/m³	M⋅L⁻¹⋅T⁻³
Radiant exposure	$H e$	joule per square metre	J/m²	M⋅T⁻²	Radiant energy received by a surface per unit area, or equivalently irradiance of a surface integrated over time of irradiation. This is sometimes also called "radiant fluence".
Spectral exposure	$H e, ν$ ^{[T2 3]}	joule per square metre per hertz	J⋅m⁻²⋅Hz⁻¹	M⋅T⁻¹	Radiant exposure of a surface per unit frequency or wavelength. The latter is commonly measured in J⋅m⁻²⋅nm⁻¹. This is sometimes also called "spectral fluence".
Spectral exposure	$H e, λ$ ^{[T2 4]}	joule per square metre, per metre	J/m³	M⋅L⁻¹⋅T⁻²
See also: SI Radiometry Photometry\|(Compare)

^ Standards organizations recommend that radiometric quantities should be denoted with suffix "e" (for "energetic") to avoid confusion with photometric or photon quantities.
^ ^2.0 ^2.1 ^2.2 ^2.3 ^2.4 Alternative symbols sometimes seen: $W$ or $E$ for radiant energy, $P$ or $F$ for radiant flux, $I$ for irradiance, $W$ for radiant exitance.
^ ^3.0 ^3.1 ^3.2 ^3.3 ^3.4 ^3.5 ^3.6 Spectral quantities given per unit frequency are denoted with suffix "ν" (Greek letter nu, not to be confused with a letter "v", indicating a photometric quantity.)
^ ^4.0 ^4.1 ^4.2 ^4.3 ^4.4 ^4.5 ^4.6 Spectral quantities given per unit wavelength are denoted with suffix "λ".
^ ^5.0 ^5.1 Directional quantities are denoted with suffix "Ω".

Table 3. SI photon units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^{[T3 1]}	Name	Symbol	Dimension	Notes
photon energy	$n$			1	count of photons $n$ with energy $Q p = h c / λ$ .^{[T3 2]}
photon flux	$Φ q$	count per second	s⁻¹	T⁻¹	photons per unit time, $d n /d t$ with $n$ = photon number. also called photon power
photon intensity	$I$	count per steradian per second	sr⁻¹⋅s⁻¹	T⁻¹	$d n /d ω$
photon radiance	$L q$	count per square metre per steradian per second	m⁻²⋅sr⁻¹⋅s⁻¹	L⁻²‍T⁻¹	$d 2 n /(d A cos(θ) d ω)$
photon irradiance	$E q$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
photon exitance	$M$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
See also: Photon counting SI Radiometry (Compare)\| Photometry\|(Compare)

^ Standards organizations recommend that photon quantities be denoted with a suffix "q" (for "quantum") to avoid confusion with radiometric and photometric quantities.
^ The energy of a single photon at wavelength $λ$ is $Q p = hc / λ$ with $h$ = Planck constant and $c$ = velocity of light.

</syntaxhighlight>

Combining the tables in a single article (combined footnotes f.e. in group "nb"):

Table 1. SI photometry quantities
v
t
e
Quantity		Unit		Dimension ^{[nb 1]}	Notes
Name	Symbol^{[nb 2]}	Name	Symbol	Dimension ^{[nb 1]}	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⁻²⋅J	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⁻²⋅J	Luminous flux incident on a surface
Luminous exitance, luminous emittance	$M v$	lumen per square metre	lm/m²	L⁻²⋅J	Luminous flux emitted from a surface
Luminous exposure	$H v$	lux second	lx⋅s	L⁻²⋅T⋅J	Time-integrated illuminance
Luminous energy density	$ω v$	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)	$η$ ^{[nb 3]}	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: SI Photometry Radiometry\|(Compare)

Table 2. SI radiometry units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^{[nb 4]}	Name	Symbol	Dimension	Notes
Radiant energy	$Q e$ ^{[nb 5]}	joule	J	M⋅L²⋅T⁻²	Energy of electromagnetic radiation.
Radiant energy density	$w e$	joule per cubic metre	J/m³	M⋅L⁻¹⋅T⁻²	Radiant energy per unit volume.
Radiant flux	$Φ e$ ^{[nb 5]}	watt	W = J/s	M⋅L²⋅T⁻³	Radiant energy emitted, reflected, transmitted or received, per unit time. This is sometimes also called "radiant power", and called luminosity in Astronomy.
Spectral flux	$Φ e, ν$ ^{[nb 6]}	watt per hertz	W/Hz	M⋅L²⋅T⁻²	Radiant flux per unit frequency or wavelength. The latter is commonly measured in W⋅nm⁻¹.
Spectral flux	$Φ e, λ$ ^{[nb 7]}	watt per metre	W/m	M⋅L⋅T⁻³
Radiant intensity	$I e,Ω$ ^{[nb 8]}	watt per steradian	W/sr	M⋅L²⋅T⁻³	Radiant flux emitted, reflected, transmitted or received, per unit solid angle. This is a directional quantity.
Spectral intensity	$I e,Ω, ν$ ^{[nb 6]}	watt per steradian per hertz	W⋅sr⁻¹⋅Hz⁻¹	M⋅L²⋅T⁻²	Radiant intensity per unit frequency or wavelength. The latter is commonly measured in W⋅sr⁻¹⋅nm⁻¹. This is a directional quantity.
Spectral intensity	$I e,Ω, λ$ ^{[nb 7]}	watt per steradian per metre	W⋅sr⁻¹⋅m⁻¹	M⋅L⋅T⁻³
Radiance	$L e,Ω$ ^{[nb 8]}	watt per steradian per square metre	W⋅sr⁻¹⋅m⁻²	M⋅T⁻³	Radiant flux emitted, reflected, transmitted or received by a surface, per unit solid angle per unit projected area. This is a directional quantity. This is sometimes also confusingly called "intensity".
Spectral radiance Specific intensity	$L e,Ω, ν$ ^{[nb 6]}	watt per steradian per square metre per hertz	W⋅sr⁻¹⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Radiance of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅sr⁻¹⋅m⁻²⋅nm⁻¹. This is a directional quantity. This is sometimes also confusingly called "spectral intensity".
Spectral radiance Specific intensity	$L e,Ω, λ$ ^{[nb 7]}	watt per steradian per square metre, per metre	W⋅sr⁻¹⋅m⁻³	M⋅L⁻¹⋅T⁻³
Irradiance Flux density	$E e$ ^{[nb 5]}	watt per square metre	W/m²	M⋅T⁻³	Radiant flux received by a surface per unit area. This is sometimes also confusingly called "intensity".
Spectral irradiance Spectral flux density	$E e, ν$ ^{[nb 6]}	watt per square metre per hertz	W⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Irradiance of a surface per unit frequency or wavelength. This is sometimes also confusingly called "spectral intensity". Non-SI units of spectral flux density include jansky (1 Jy = 10⁻²⁶ W⋅m⁻²⋅Hz⁻¹) and solar flux unit (1 sfu = 10⁻²² W⋅m⁻²⋅Hz⁻¹ = 10⁴ Jy).
Spectral irradiance Spectral flux density	$E e, λ$ ^{[nb 7]}	watt per square metre, per metre	W/m³	M⋅L⁻¹⋅T⁻³
Radiosity	$J e$ ^{[nb 5]}	watt per square metre	W/m²	M⋅T⁻³	Radiant flux leaving (emitted, reflected and transmitted by) a surface per unit area. This is sometimes also confusingly called "intensity".
Spectral radiosity	$J e, ν$ ^{[nb 6]}	watt per square metre per hertz	W⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Radiosity of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m⁻²⋅nm⁻¹. This is sometimes also confusingly called "spectral intensity".
Spectral radiosity	$J e, λ$ ^{[nb 7]}	watt per square metre, per metre	W/m³	M⋅L⁻¹⋅T⁻³
Radiant exitance	$M e$ ^{[nb 5]}	watt per square metre	W/m²	M⋅T⁻³	Radiant flux emitted by a surface per unit area. This is the emitted component of radiosity. "Radiant emittance" is an old term for this quantity. This is sometimes also confusingly called "intensity".
Spectral exitance	$M e, ν$ ^{[nb 6]}	watt per square metre per hertz	W⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Radiant exitance of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m⁻²⋅nm⁻¹. "Spectral emittance" is an old term for this quantity. This is sometimes also confusingly called "spectral intensity".
Spectral exitance	$M e, λ$ ^{[nb 7]}	watt per square metre, per metre	W/m³	M⋅L⁻¹⋅T⁻³
Radiant exposure	$H e$	joule per square metre	J/m²	M⋅T⁻²	Radiant energy received by a surface per unit area, or equivalently irradiance of a surface integrated over time of irradiation. This is sometimes also called "radiant fluence".
Spectral exposure	$H e, ν$ ^{[nb 6]}	joule per square metre per hertz	J⋅m⁻²⋅Hz⁻¹	M⋅T⁻¹	Radiant exposure of a surface per unit frequency or wavelength. The latter is commonly measured in J⋅m⁻²⋅nm⁻¹. This is sometimes also called "spectral fluence".
Spectral exposure	$H e, λ$ ^{[nb 7]}	joule per square metre, per metre	J/m³	M⋅L⁻¹⋅T⁻²
See also: SI Radiometry Photometry\|(Compare)

Table 3. SI photon units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^{[nb 9]}	Name	Symbol	Dimension	Notes
photon energy	$n$			1	count of photons $n$ with energy $Q p = h c / λ$ .^{[nb 10]}
photon flux	$Φ q$	count per second	s⁻¹	T⁻¹	photons per unit time, $d n /d t$ with $n$ = photon number. also called photon power
photon intensity	$I$	count per steradian per second	sr⁻¹⋅s⁻¹	T⁻¹	$d n /d ω$
photon radiance	$L q$	count per square metre per steradian per second	m⁻²⋅sr⁻¹⋅s⁻¹	L⁻²‍T⁻¹	$d 2 n /(d A cos(θ) d ω)$
photon irradiance	$E q$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
photon exitance	$M$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
See also: Photon counting SI Radiometry (Compare)\| Photometry\|(Compare)

...

^ 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
^ ^3.0 ^3.1 ^3.2 Alternative symbols sometimes seen: $W$ for luminous energy, $P$ or $F$ for luminous flux, and $ρ$ for luminous efficacy of a source.
^ Standards organizations recommend that radiometric quantities should be denoted with suffix "e" (for "energetic") to avoid confusion with photometric or photon quantities.
^ ^5.0 ^5.1 ^5.2 ^5.3 ^5.4 Alternative symbols sometimes seen: $W$ or $E$ for radiant energy, $P$ or $F$ for radiant flux, $I$ for irradiance, $W$ for radiant exitance.
^ ^6.0 ^6.1 ^6.2 ^6.3 ^6.4 ^6.5 ^6.6 Spectral quantities given per unit frequency are denoted with suffix "ν" (Greek letter nu, not to be confused with a letter "v", indicating a photometric quantity.)
^ ^7.0 ^7.1 ^7.2 ^7.3 ^7.4 ^7.5 ^7.6 Spectral quantities given per unit wavelength are denoted with suffix "λ".
^ ^8.0 ^8.1 Directional quantities are denoted with suffix "Ω".
^ Standards organizations recommend that photon quantities be denoted with a suffix "q" (for "quantum") to avoid confusion with radiometric and photometric quantities.
^ The energy of a single photon at wavelength $λ$ is $Q p = hc / λ$ with $h$ = Planck constant and $c$ = velocity of light.

</syntaxhighlight>

Combining the tables in a single article (combined footnotes with default references):

Table 1. SI photometry quantities
v
t
e
Quantity		Unit		Dimension ^[3]	Notes
Name	Symbol^[4]	Name	Symbol	Dimension ^[3]	Notes
Luminous energy	$Q v$ ^[5]	lumen second	lm⋅s	T⋅J	The lumen second is sometimes called the talbot.
Luminous flux, luminous power	$Φ v$ ^[5]	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⁻²⋅J	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⁻²⋅J	Luminous flux incident on a surface
Luminous exitance, luminous emittance	$M v$	lumen per square metre	lm/m²	L⁻²⋅J	Luminous flux emitted from a surface
Luminous exposure	$H v$	lux second	lx⋅s	L⁻²⋅T⋅J	Time-integrated illuminance
Luminous energy density	$ω v$	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)	$η$ ^[5]	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: SI Photometry Radiometry\|(Compare)

Table 2. SI radiometry units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^[6]	Name	Symbol	Dimension	Notes
Radiant energy	$Q e$ ^[7]	joule	J	M⋅L²⋅T⁻²	Energy of electromagnetic radiation.
Radiant energy density	$w e$	joule per cubic metre	J/m³	M⋅L⁻¹⋅T⁻²	Radiant energy per unit volume.
Radiant flux	$Φ e$ ^[7]	watt	W = J/s	M⋅L²⋅T⁻³	Radiant energy emitted, reflected, transmitted or received, per unit time. This is sometimes also called "radiant power", and called luminosity in Astronomy.
Spectral flux	$Φ e, ν$ ^[8]	watt per hertz	W/Hz	M⋅L²⋅T⁻²	Radiant flux per unit frequency or wavelength. The latter is commonly measured in W⋅nm⁻¹.
Spectral flux	$Φ e, λ$ ^[9]	watt per metre	W/m	M⋅L⋅T⁻³
Radiant intensity	$I e,Ω$ ^[10]	watt per steradian	W/sr	M⋅L²⋅T⁻³	Radiant flux emitted, reflected, transmitted or received, per unit solid angle. This is a directional quantity.
Spectral intensity	$I e,Ω, ν$ ^[8]	watt per steradian per hertz	W⋅sr⁻¹⋅Hz⁻¹	M⋅L²⋅T⁻²	Radiant intensity per unit frequency or wavelength. The latter is commonly measured in W⋅sr⁻¹⋅nm⁻¹. This is a directional quantity.
Spectral intensity	$I e,Ω, λ$ ^[9]	watt per steradian per metre	W⋅sr⁻¹⋅m⁻¹	M⋅L⋅T⁻³
Radiance	$L e,Ω$ ^[10]	watt per steradian per square metre	W⋅sr⁻¹⋅m⁻²	M⋅T⁻³	Radiant flux emitted, reflected, transmitted or received by a surface, per unit solid angle per unit projected area. This is a directional quantity. This is sometimes also confusingly called "intensity".
Spectral radiance Specific intensity	$L e,Ω, ν$ ^[8]	watt per steradian per square metre per hertz	W⋅sr⁻¹⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Radiance of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅sr⁻¹⋅m⁻²⋅nm⁻¹. This is a directional quantity. This is sometimes also confusingly called "spectral intensity".
Spectral radiance Specific intensity	$L e,Ω, λ$ ^[9]	watt per steradian per square metre, per metre	W⋅sr⁻¹⋅m⁻³	M⋅L⁻¹⋅T⁻³
Irradiance Flux density	$E e$ ^[7]	watt per square metre	W/m²	M⋅T⁻³	Radiant flux received by a surface per unit area. This is sometimes also confusingly called "intensity".
Spectral irradiance Spectral flux density	$E e, ν$ ^[8]	watt per square metre per hertz	W⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Irradiance of a surface per unit frequency or wavelength. This is sometimes also confusingly called "spectral intensity". Non-SI units of spectral flux density include jansky (1 Jy = 10⁻²⁶ W⋅m⁻²⋅Hz⁻¹) and solar flux unit (1 sfu = 10⁻²² W⋅m⁻²⋅Hz⁻¹ = 10⁴ Jy).
Spectral irradiance Spectral flux density	$E e, λ$ ^[9]	watt per square metre, per metre	W/m³	M⋅L⁻¹⋅T⁻³
Radiosity	$J e$ ^[7]	watt per square metre	W/m²	M⋅T⁻³	Radiant flux leaving (emitted, reflected and transmitted by) a surface per unit area. This is sometimes also confusingly called "intensity".
Spectral radiosity	$J e, ν$ ^[8]	watt per square metre per hertz	W⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Radiosity of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m⁻²⋅nm⁻¹. This is sometimes also confusingly called "spectral intensity".
Spectral radiosity	$J e, λ$ ^[9]	watt per square metre, per metre	W/m³	M⋅L⁻¹⋅T⁻³
Radiant exitance	$M e$ ^[7]	watt per square metre	W/m²	M⋅T⁻³	Radiant flux emitted by a surface per unit area. This is the emitted component of radiosity. "Radiant emittance" is an old term for this quantity. This is sometimes also confusingly called "intensity".
Spectral exitance	$M e, ν$ ^[8]	watt per square metre per hertz	W⋅m⁻²⋅Hz⁻¹	M⋅T⁻²	Radiant exitance of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m⁻²⋅nm⁻¹. "Spectral emittance" is an old term for this quantity. This is sometimes also confusingly called "spectral intensity".
Spectral exitance	$M e, λ$ ^[9]	watt per square metre, per metre	W/m³	M⋅L⁻¹⋅T⁻³
Radiant exposure	$H e$	joule per square metre	J/m²	M⋅T⁻²	Radiant energy received by a surface per unit area, or equivalently irradiance of a surface integrated over time of irradiation. This is sometimes also called "radiant fluence".
Spectral exposure	$H e, ν$ ^[8]	joule per square metre per hertz	J⋅m⁻²⋅Hz⁻¹	M⋅T⁻¹	Radiant exposure of a surface per unit frequency or wavelength. The latter is commonly measured in J⋅m⁻²⋅nm⁻¹. This is sometimes also called "spectral fluence".
Spectral exposure	$H e, λ$ ^[9]	joule per square metre, per metre	J/m³	M⋅L⁻¹⋅T⁻²
See also: SI Radiometry Photometry\|(Compare)

Table 3. SI photon units
v
t
e
Quantity		Unit		Dimension	Notes
Name	Symbol^[1]	Name	Symbol	Dimension	Notes
photon energy	$n$			1	count of photons $n$ with energy $Q p = h c / λ$ .^[2]
photon flux	$Φ q$	count per second	s⁻¹	T⁻¹	photons per unit time, $d n /d t$ with $n$ = photon number. also called photon power
photon intensity	$I$	count per steradian per second	sr⁻¹⋅s⁻¹	T⁻¹	$d n /d ω$
photon radiance	$L q$	count per square metre per steradian per second	m⁻²⋅sr⁻¹⋅s⁻¹	L⁻²‍T⁻¹	$d 2 n /(d A cos(θ) d ω)$
photon irradiance	$E q$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
photon exitance	$M$	count per square metre per second	m⁻²⋅s⁻¹	L⁻²‍T⁻¹	$d n /d A$
See also: Photon counting SI Radiometry (Compare)\| Photometry\|(Compare)

...

^ ^1.0 ^1.1 ^1.2 ^1.3 Standards organizations recommend that photon quantities be denoted with a suffix "q" (for "quantum") to avoid confusion with radiometric and photometric quantities.
^ ^2.0 ^2.1 ^2.2 ^2.3 The energy of a single photon at wavelength $λ$ is $Q p = hc / λ$ with $h$ = Planck constant and $c$ = velocity of light.
^ 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
^ ^5.0 ^5.1 ^5.2 Alternative symbols sometimes seen: $W$ for luminous energy, $P$ or $F$ for luminous flux, and $ρ$ for luminous efficacy of a source.
^ Standards organizations recommend that radiometric quantities should be denoted with suffix "e" (for "energetic") to avoid confusion with photometric or photon quantities.
^ ^7.0 ^7.1 ^7.2 ^7.3 ^7.4 Alternative symbols sometimes seen: $W$ or $E$ for radiant energy, $P$ or $F$ for radiant flux, $I$ for irradiance, $W$ for radiant exitance.
^ ^8.0 ^8.1 ^8.2 ^8.3 ^8.4 ^8.5 ^8.6 Spectral quantities given per unit frequency are denoted with suffix "ν" (Greek letter nu, not to be confused with a letter "v", indicating a photometric quantity.)
^ ^9.0 ^9.1 ^9.2 ^9.3 ^9.4 ^9.5 ^9.6 Spectral quantities given per unit wavelength are denoted with suffix "λ".
^ ^10.0 ^10.1 Directional quantities are denoted with suffix "Ω".

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Notes

Ideally, the "(Compare)" links would show up on the left or right of the table header, similar to "v d e", so that the cursor would remain in the same position and one could flip back and forth between the tables without window realignment. However, this would require a small change in the {{Navbar-header}} template.

Usage

Parameters

Parameter 1

Parameter 2

Parameter 3

Examples

Notes

See also