colour_hdri.utilities.exposure Module

Image Exposure Value Computation

Defines image exposure value computation objects:

colour_hdri.utilities.exposure.exposure_value(f_number, exposure_time, iso)[source]

Computes the exposure value from given image FNumber, Exposure Time and ISO values.

Parameters:
  • f_number (array_like) – Image FNumber.
  • exposure_time (array_like) – Image Exposure Time.
  • iso (array_like) – Image ISO.
Returns:

Image exposure value.
Return type:

ndarray

Examples

>>> exposure_value(8, 1, 100)
6.0
colour_hdri.utilities.exposure.adjust_exposure(a, EV)[source]

Adjusts given array exposure using given \(EV\) exposure value.

Parameters:
  • a (array_like) – Array to adjust the exposure.
  • EV (numeric) – Exposure adjustment value.
Returns:

Exposure adjusted array.
Return type:

ndarray

Examples

>>> adjust_exposure(np.array([0.25, 0.5, 0.75, 1]), 1)
array([ 0.5,  1. ,  1.5,  2. ])
colour_hdri.utilities.exposure.average_luminance(f_number, exposure_time, iso, k=12.5)[source]

Computes the average luminance from given image FNumber, Exposure Time and ISO values.

Parameters:
  • f_number (array_like) – Image FNumber.
  • exposure_time (array_like) – Image Exposure Time.
  • iso (array_like) – Image ISO.
  • k (numeric, optional) – Reflected light calibration constant \(K\).
Returns:

Image average luminance.
Return type:

ndarray

References

[1]Wikipedia. (n.d.). EV as a measure of luminance and illuminance. Retrieved November 14, 2015, from https://en.wikipedia.org/wiki/Exposure_value#EV_as_a_measure_of_luminance_and_illuminance

Examples

>>> average_luminance(8, 1, 100)
0.125