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# 8.2 Summary of radiometric and photometric quantities

 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 – Φe Φλ(λ) Φv W W nm-1 lm (lumen) emitted in a certain direction radiant intensity spectral radiant intensity luminous intensity direction Ie Iλ(λ) Iv W sr-1 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 Me Mλ(λ) Mv 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 Le Lλ(λ) Lv 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 Ee Eλ(λ) Ev W m-2 W m-2 nm-1 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:

 Xe = ∞ ∫ Xλ(λ) dλ 0

or

 Xe,range = λ2 ∫ Xλ(λ) dλ λ1

with λ1 and λ2 denoting the lower and the upper limit of the respective wavelength range (for instance, UV-A).

### Photometric quantities

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

#### Photopic vision

 Xv = Km × ∞ ∫ Xλ(λ) × V(λ)dλ with Km = 683 lm / W 0

#### Scotopic vision

 Xv = K'm × ∞ ∫ Xλ(λ) × V'(λ)dλ with K'm = 1700 lm / W 0

### Basic integral relations between radiometric and photometric quantities

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

 Φx = ∫ Ix dΩ 4π
 Ix = ∫ Lx cos(ϑ) dA emitting surface
 Mx = ∫ Lx cos(ϑ) dΩ 2π