colour_hdri.average_luminance

colour_hdri.average_luminance(N, t, S, k=12.5)

Computes the average luminance \(L\) in \(cd\cdot m^{-2}\) from given relative aperture F-Number \(N\), Exposure Time \(t\), ISO arithmetic speed \(S\) and reflected light calibration constant \(k\).

Parameters

• N (array_like) – Relative aperture F-Number \(N\).

• t (array_like) – Exposure Time \(t\).

• S (array_like) – ISO arithmetic speed \(S\).

• k (numeric, optional) – Reflected light calibration constant \(k\). ISO 2720:1974 recommends a range for \(k\) of 10.6 to 13.4 with luminance in \(cd\cdot m^{-2}\). Two values for \(k\) are in common use: 12.5 (Canon, Nikon, and Sekonic) and 14 (Minolta, Kenko, and Pentax).

Returns

Average luminance \(L\) in \(cd\cdot m^{-2}\).

Return type

ndarray

References

[Wikipediaa]

Examples

>>> average_luminance(8, 1, 100)
8.0