colour_hdri.arithmetic_mean_focal_plane_exposure¶
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colour_hdri.arithmetic_mean_focal_plane_exposure(L_a, A, t)[source]¶ Computes 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 (array_like) – Arithmetic scene luminance \(L_a\), expressed in \(cd/m^2\).
A (array_like) – Lens F-Number \(A\).
t (array_like) – Exposure Time \(t\), expressed in seconds.
- Returns
Focal plane exposure \(H_a\).
- Return type
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
Examples
>>> arithmetic_mean_focal_plane_exposure(4000, 8, 1 / 250) ... 0.1628937...