colour_hdri.average_illuminance#

colour_hdri.average_illuminance(N: ArrayLike, t: ArrayLike, S: ArrayLike, c: ArrayLike = 250) → NDArrayFloat[source]#

Compute the average illuminance \(E\) in \(Lux\) from given relative aperture F-Number \(N\), Exposure Time \(t\), ISO arithmetic speed \(S\) and incident light calibration constant \(c\).

Parameters:

N (ArrayLike) – Relative aperture F-Number \(N\).
t (ArrayLike) – Exposure Time \(t\).
S (ArrayLike) – ISO arithmetic speed \(S\).
c (ArrayLike) – Incident light calibration constant \(c\). With a flat receptor, ISO 2720:1974 recommends a range for \(c\). of 240 to 400 with illuminance in \(Lux\); a value of 250 is commonly used. With a hemispherical receptor, ISO 2720:1974 recommends a range for \(c\) of 320 to 540 with illuminance in \(Lux\); in practice, values typically are between 320 (Minolta) and 340 (Sekonic).

Returns:

Average illuminance \(E\) in \(Lux\).

Return type:

numpy.ndarray

References

[Wikipediab]

Examples

>>> average_illuminance(8, 1, 100)
160.0