# -*- coding: utf-8 -*-
"""
Photometry
==========
Defines photometric quantities computation related objects.
References
----------
- :cite:`Wikipedia2003b` : Wikipedia. (2003). Luminosity function. Retrieved
October 20, 2014, from
https://en.wikipedia.org/wiki/Luminosity_function#Details
- :cite:`Wikipedia2005c` : Wikipedia. (2005). Luminous Efficacy. Retrieved
April 3, 2016, from https://en.wikipedia.org/wiki/Luminous_efficacy
"""
from __future__ import division, unicode_literals
import numpy as np
from colour.colorimetry import SDS_LEFS_PHOTOPIC
from colour.constants import CONSTANT_K_M
from colour.utilities import as_float
__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2020 - Colour Developers'
__license__ = 'New BSD License - https://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-developers@colour-science.org'
__status__ = 'Production'
__all__ = ['luminous_flux', 'luminous_efficiency', 'luminous_efficacy']
[docs]def luminous_flux(sd,
lef=SDS_LEFS_PHOTOPIC['CIE 1924 Photopic Standard Observer'],
K_m=CONSTANT_K_M):
"""
Returns the *luminous flux* for given spectral distribution using given
luminous efficiency function.
Parameters
----------
sd : SpectralDistribution
test spectral distribution
lef : SpectralDistribution, 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:`Wikipedia2003b`
Examples
--------
>>> from colour import SDS_LIGHT_SOURCES
>>> sd = SDS_LIGHT_SOURCES['Neodimium Incandescent']
>>> luminous_flux(sd) # doctest: +ELLIPSIS
23807.6555273...
"""
lef = lef.copy().align(
sd.shape,
extrapolator_kwargs={
'method': 'Constant',
'left': 0,
'right': 0
})
sd = sd.copy() * lef
flux = K_m * np.trapz(sd.values, sd.wavelengths)
return as_float(flux)
[docs]def luminous_efficiency(
sd, lef=SDS_LEFS_PHOTOPIC['CIE 1924 Photopic Standard Observer']):
"""
Returns the *luminous efficiency* of given spectral distribution using
given luminous efficiency function.
Parameters
----------
sd : SpectralDistribution
test spectral distribution
lef : SpectralDistribution, optional
:math:`V(\\lambda)` luminous efficiency function.
Returns
-------
numeric
Luminous efficiency.
References
----------
:cite:`Wikipedia2003b`
Examples
--------
>>> from colour import SDS_LIGHT_SOURCES
>>> sd = SDS_LIGHT_SOURCES['Neodimium Incandescent']
>>> luminous_efficiency(sd) # doctest: +ELLIPSIS
0.1994393...
"""
lef = lef.copy().align(
sd.shape,
extrapolator_kwargs={
'method': 'Constant',
'left': 0,
'right': 0
})
sd = sd.copy()
efficiency = (np.trapz(lef.values * sd.values, sd.wavelengths) / np.trapz(
sd.values, sd.wavelengths))
return efficiency
[docs]def luminous_efficacy(
sd, lef=SDS_LEFS_PHOTOPIC['CIE 1924 Photopic Standard Observer']):
"""
Returns the *luminous efficacy* in :math:`lm\\cdot W^{-1}` of given
spectral distribution using given luminous efficiency function.
Parameters
----------
sd : SpectralDistribution
test spectral distribution
lef : SpectralDistribution, optional
:math:`V(\\lambda)` luminous efficiency function.
Returns
-------
numeric
Luminous efficacy in :math:`lm\\cdot W^{-1}`.
References
----------
:cite:`Wikipedia2005c`
Examples
--------
>>> from colour import SDS_LIGHT_SOURCES
>>> sd = SDS_LIGHT_SOURCES['Neodimium Incandescent']
>>> luminous_efficacy(sd) # doctest: +ELLIPSIS
136.2170803...
"""
efficacy = CONSTANT_K_M * luminous_efficiency(sd, lef)
return as_float(efficacy)