#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
Photometry
==========
Defines photometric quantities computation related objects.
See Also
--------
`Photometry IPython Notebook
<http://nbviewer.ipython.org/github/colour-science/colour-ipython/\
blob/master/notebooks/colorimetry/photometry.ipynb>`_
References
----------
.. [1] Wikipedia. (n.d.). Luminosity function. Retrieved October 20, 2014,
from https://en.wikipedia.org/wiki/Luminosity_function#Details
.. [2] Ohno, Y., & Davis, W. (2008). NIST CQS simulation 7.4. Retrieved from
http://cie2.nist.gov/TC1-69/NIST CQS simulation 7.4.xls
"""
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 - 2015 - 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_efficacy']
[docs]def luminous_flux(spd,
lef=PHOTOPIC_LEFS.get(
'CIE 1924 Photopic Standard Observer'),
K_m=K_M):
"""
Returns the *luminous flux* for given spectral power distribution using
the 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
Examples
--------
>>> from colour import LIGHT_SOURCES_RELATIVE_SPDS
>>> spd = LIGHT_SOURCES_RELATIVE_SPDS.get('Neodimium Incandescent')
>>> luminous_flux(spd) # doctest: +ELLIPSIS
23807.6555273...
"""
lef = lef.clone().align(spd.shape, left=0, right=0)
spd = spd.clone() * lef
flux = K_m * np.trapz(spd.values, spd.wavelengths)
return flux
[docs]def luminous_efficacy(spd,
lef=PHOTOPIC_LEFS.get(
'CIE 1924 Photopic Standard Observer')):
"""
Returns the *luminous efficacy* for given spectral power distribution using
the given luminous efficiency function.
Parameters
----------
spd : SpectralPowerDistribution
test spectral power distribution
lef : SpectralPowerDistribution, optional
:math:`V(\lambda)` luminous efficiency function.
Returns
-------
numeric
Luminous efficacy
Examples
--------
>>> from colour import LIGHT_SOURCES_RELATIVE_SPDS
>>> spd = LIGHT_SOURCES_RELATIVE_SPDS.get('Neodimium Incandescent')
>>> luminous_efficacy(spd) # doctest: +ELLIPSIS
0.1994393...
"""
lef = lef.clone().align(spd.shape, left=0, right=0)
spd = spd.clone()
efficacy = (np.trapz(lef.values * spd.values, spd.wavelengths) /
np.trapz(spd.values, spd.wavelengths))
return efficacy