# -*- coding: utf-8 -*-
"""
Photometry
==========
Defines photometric quantities computation related objects.
See Also
--------
`Photometry Jupyter Notebook
<http://nbviewer.jupyter.org/github/colour-science/colour-notebooks/\
blob/master/notebooks/colorimetry/photometry.ipynb>`_
References
----------
- :cite:`Wikipediacm` : Wikipedia. (n.d.). Luminous Efficacy. Retrieved April
3, 2016, from https://en.wikipedia.org/wiki/Luminous_efficacy
- :cite:`Wikipediacq` : Wikipedia. (n.d.). Luminosity function. Retrieved
October 20, 2014, from https://en.wikipedia.org/wiki/\
Luminosity_function#Details
"""
from __future__ import division, unicode_literals
import numpy as np
from colour.colorimetry import PHOTOPIC_LEFS
from colour.constants import K_M
__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2018 - Colour Developers'
__license__ = 'New BSD License - http://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-science@googlegroups.com'
__status__ = 'Production'
__all__ = ['luminous_flux', 'luminous_efficiency', 'luminous_efficacy']
[docs]def luminous_flux(spd,
lef=PHOTOPIC_LEFS['CIE 1924 Photopic Standard Observer'],
K_m=K_M):
"""
Returns the *luminous flux* for given spectral power distribution using
given luminous efficiency function.
Parameters
----------
spd : SpectralPowerDistribution
test spectral power distribution
lef : SpectralPowerDistribution, optional
:math:`V(\lambda)` luminous efficiency function.
K_m : numeric, optional
:math:`lm\cdot W^{-1}` maximum photopic luminous efficiency
Returns
-------
numeric
Luminous flux.
References
----------
- :cite:`Wikipediacq`
Examples
--------
>>> from colour import LIGHT_SOURCES_RELATIVE_SPDS
>>> spd = LIGHT_SOURCES_RELATIVE_SPDS['Neodimium Incandescent']
>>> luminous_flux(spd) # doctest: +ELLIPSIS
23807.6555273...
"""
lef = lef.copy().align(
spd.shape,
extrapolator_args={'method': 'Constant',
'left': 0,
'right': 0})
spd = spd.copy() * lef
flux = K_m * np.trapz(spd.values, spd.wavelengths)
return flux
[docs]def luminous_efficiency(
spd, lef=PHOTOPIC_LEFS['CIE 1924 Photopic Standard Observer']):
"""
Returns the *luminous efficiency* of given spectral power distribution
using given luminous efficiency function.
Parameters
----------
spd : SpectralPowerDistribution
test spectral power distribution
lef : SpectralPowerDistribution, optional
:math:`V(\lambda)` luminous efficiency function.
Returns
-------
numeric
Luminous efficiency.
References
----------
- :cite:`Wikipediacq`
Examples
--------
>>> from colour import LIGHT_SOURCES_RELATIVE_SPDS
>>> spd = LIGHT_SOURCES_RELATIVE_SPDS['Neodimium Incandescent']
>>> luminous_efficiency(spd) # doctest: +ELLIPSIS
0.1994393...
"""
lef = lef.copy().align(
spd.shape,
extrapolator_args={'method': 'Constant',
'left': 0,
'right': 0})
spd = spd.copy()
efficiency = (np.trapz(lef.values * spd.values, spd.wavelengths) /
np.trapz(spd.values, spd.wavelengths))
return efficiency
[docs]def luminous_efficacy(
spd, lef=PHOTOPIC_LEFS['CIE 1924 Photopic Standard Observer']):
"""
Returns the *luminous efficacy* in :math:`lm\cdot W^{-1}` of given spectral
power distribution using given luminous efficiency function.
Parameters
----------
spd : SpectralPowerDistribution
test spectral power distribution
lef : SpectralPowerDistribution, optional
:math:`V(\lambda)` luminous efficiency function.
Returns
-------
numeric
Luminous efficacy in :math:`lm\cdot W^{-1}`.
References
----------
- :cite:`Wikipediacm`
Examples
--------
>>> from colour import LIGHT_SOURCES_RELATIVE_SPDS
>>> spd = LIGHT_SOURCES_RELATIVE_SPDS['Neodimium Incandescent']
>>> luminous_efficacy(spd) # doctest: +ELLIPSIS
136.2170803...
"""
efficacy = K_M * luminous_efficiency(spd, lef)
return efficacy