colour_hdri.focal_plane_exposure

colour_hdri.focal_plane_exposure(L, A, t, F, i, H_f, T=0.9, f_v=0.98, theta=10)[source]

Computes the focal plane exposure \(H\) in lux-seconds (\(lx.s\)).

Parameters

  • L (array_like) – Scene luminance \(L\), expressed in \(cd/m^2\).

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

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

  • F (array_like) – Lens focal length \(F\), expressed in meters.

  • i (array_like) – Image distance \(i\), expressed in meters.

  • H_f (array_like) – Focal plane flare exposure \(H_f\), expressed in lux-seconds (\(lx.s\)).

  • T (array_like, optional) – Transmission factor of the lens \(T\).

  • f_v (array_like, optional) – Vignetting factor \(f_v\).

  • theta (array_like, optional) – Angle of image point off axis \(\theta\).

Returns

Focal plane exposure \(H\) in lux-seconds (\(lx.s\)).

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

[ISO06]

Examples

>>> focal_plane_exposure(4000, 8, 1 / 250, 50 / 1000, 50 / 1000, 0.0015)
... 
0.1643937...