Quantification of electromagnetic radiation … |
Radiometric quantity |
Spectral quantity |
Photometric quantity |
Quantity depends on |

emitted by a source in total |
radiant power |
spectral radiant power |
luminous flux |
– |

Φ |
Φ |
Φ_{v} |
||

W |
W nm^{-1} |
lm (lumen) | ||

emitted in a certain direction |
radiant intensity |
spectral radiant intensity |
luminous intensity |
direction |

I_{e} |
I_{λ}(λ) |
I_{v} |
||

W sr |
W sr^{-1} nm^{-1} |
lm / sr = cd |
||

emitted by a location on a surface |
radiant exitance |
spectral radiant exitance |
luminous exitance |
position on source’s surface |

M_{e} |
M_{λ}(λ) |
M_{v} |
||

W m^{-2} |
W m^{-2} nm^{-1} |
lm m^{-2} |
||

emitted by a location on a surface in a certain direction |
radiance |
spectral radiance |
luminance |
direction and position on source’s surface |

L_{e} |
L_{λ}(λ) |
L_{v} |
||

W sr^{-1} m^{-2} |
W sr^{-1} m^{-2} nm^{-1} |
lm sr^{-1} m^{-2} = cd m^{-2} |
||

impinging upon a surface |
irradiance |
spectral irradiance |
illuminance |
position on irradiated surface |

E_{e} |
E_{λ}(λ) |
E_{v} |
||

W m |
W m |
lm m^{-2} = lx |

*Tab. 1: Radiometric and photometric quantities*

In the following relations, X has to be replaced with one of the symbols Φ, I, L or E:

X _{e}=∞ ∫ X _{λ}(λ) dλ0

or

X _{e,range}=λ _{2}∫ X _{λ}(λ) dλλ _{1}

with λ_{1} and λ_{2} denoting the lower and the upper limit of the respective wavelength range (for instance, UV-A).

In the following relations, X has to be replaced with one of the symbols Φ, I, L or E:

X _{v}= K_{m}×∞ ∫ X _{λ}(λ) × V(λ)dλ with K_{m}= 683 lm / W0

X _{v}= K'_{m}×∞ ∫ X _{λ}(λ) × V'(λ)dλ with K'_{m}= 1700 lm / W0

In the following, x has to be replaced either with e (denoting radiometric quantities) or v (denoting photometric quantities).

Φ _{x}=∫ I _{x}dΩ4π

I _{x}=∫ L _{x}cos(ϑ) dAemitting surface

M _{x}=∫ L _{x}cos(ϑ) dΩ2π