colour_hdri.average_luminance#

colour_hdri.average_luminance(N: ArrayLike, t: ArrayLike, S: ArrayLike, k: ArrayLike = 12.5) → NDArrayFloat[source]#

Compute 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 (ArrayLike) – Relative aperture F-Number \(N\).

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

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

  • k (ArrayLike) – 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:

numpy.ndarray

References

[Wikipediab]

Examples

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