Editing Luminous intensity (section)

==Usage==
[[file:Luminosity.svg |thumb |[[Photopic vision|Photopic]] (black) and [[scotopic vision|scotopic]] (green) luminosity functions.<ref name="scvl" group=c/> The photopic includes the CIE 1931 standard<ref name="ciexyz31" group=c/><ref name="ciexyz31_curve" group=c/> (solid), the Judd–Vos 1978 modified data<ref name="vljv" group=c/> (dashed), and the Sharpe, Stockman, Jagla & Jägle 2005 data<ref name="ssvl2" group=c/> (dotted). The horizontal axis is wavelength in [[Nanometre|nm]].]]
The luminous intensity for monochromatic light of a particular wavelength {{mvar|λ}} is given by
<math display="block">I_\mathrm{v} = 683 \cdot \overline{y}(\lambda) \cdot I_\mathrm{e},</math>
where
* {{math|''I''<sub>v</sub>}} is the luminous intensity in candelas&nbsp;(cd),
* {{math|''I''<sub>e</sub>}} is the [[radiant intensity]] in watts per steradian&nbsp;(W/sr),
* <math display="inline"> \overline{y}(\lambda)</math> is the [[Luminosity function|standard luminosity function]].

If more than one wavelength is present (as is usually the case), one must sum or integrate over the [[spectrum]] of wavelengths present to get the luminous intensity:

<math display="block">I_\mathrm{v} = 683 \int_0^\infty \overline{y}(\lambda) \cdot \frac{\partial I_{\mathrm{e}}}{\partial \lambda} \, d\lambda.</math>