colour_hdri.arithmetic_mean_focal_plane_exposure#

colour_hdri.arithmetic_mean_focal_plane_exposure(L_a: ArrayLike, A: ArrayLike, t: ArrayLike) → NDArrayFloat[source]#

Compute the arithmetic mean focal plane exposure \(H_a\) for a camera focused on infinity, \(H_f << H\), \(T=9/10\), \(\theta =10^{\circ}\) and \(f_v=98/100\).

Parameters:

  • L_a (ArrayLike) – Arithmetic scene luminance \(L_a\), expressed in \(cd/m^2\).

  • A (ArrayLike) – Lens F-Number \(A\).

  • t (ArrayLike) – Exposure Time \(t\), expressed in seconds.

Returns:

Focal plane exposure \(H_a\).

Return type:

numpy.ndarray

Notes

  • Focal plane exposure is also named luminous exposure or photometric exposure and is time-integrated illuminance.

  • Object distance \(o\), focal length \(F\), and image distance \(i\) are related by the thin-lens equation: \(\cfrac{1}{f}=\cfrac{1}{o}+\cfrac{1}{i}\)

  • This method ignores the ISO arithmetic speed \(S\) and is not concerned with determining an appropriate minimum or maximum exposure level.

References

[ISO06]

Examples

>>> arithmetic_mean_focal_plane_exposure(4000, 8, 1 / 250)
... 
0.1628937...
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