colour.colorimetry.luminance Module¶

Luminance $Y$¶

Defines luminance $Y$ computation objects.

The following methods are available:

• luminance_newhall1943(): luminance $Y$ computation of given Munsell value $V$ using Newhall, Nickerson, and Judd (1943) method.
• luminance_1976(): luminance $Y$ computation of given Lightness $L^*$ as per CIE Lab implementation.
• luminance_ASTM_D1535_08(): luminance $Y$ computation of given Munsell value $V$ using ASTM D1535-08e1 (2008) method.

colour.colorimetry.luminance.luminance_newhall1943(V, **kwargs)[source]¶

Returns the luminance $Y$ of given Munsell value $V$ using Newhall, Nickerson, and Judd (1943) method.

Parameters:	V (numeric) – Munsell value $V$. **kwargs (**, optional) – Unused parameter provided for signature compatibility with other luminance computation objects.
Returns:	luminance $Y$.
Return type:	numeric

Notes

• Input Munsell value $V$ is in domain [0, 10].
• Output luminance $Y$ is in domain [0, 100].

References

[1]	http://en.wikipedia.org/wiki/Lightness (Last accessed 13 April 2014)

Examples

>>> luminance_newhall1943(3.74629715382)  
10.4089874...

colour.colorimetry.luminance.luminance_1976(L, Yn=100)[source]¶

Returns the luminance $Y$ of given Lightness $L^*$ with given reference white luminance $Y_n$.

Parameters:	L (numeric) – Lightness $L^*$ Yn (numeric) – White reference luminance $Y_n$.
Returns:	luminance $Y$.
Return type:	numeric

Notes

• Input Lightness $L^*$ is in domain [0, 100].
• Output luminance $Y$ is in domain [0, 100].

References

[2]	http://www.poynton.com/PDFs/GammaFAQ.pdf (Last accessed 12 April 2014)

Examples

>>> luminance_1976(37.9856290977)  
10.0800000...

colour.colorimetry.luminance.luminance_ASTM_D1535_08(V, **kwargs)[source]¶

Returns the luminance $Y$ of given Munsell value $V$ using ASTM D1535-08e1 (2008) method.

Parameters:	V (numeric) – Munsell value $V$. **kwargs (**, optional) – Unused parameter provided for signature compatibility with other luminance computation objects.
Returns:	luminance $Y$.
Return type:	numeric

Notes

• Input Munsell value $V$ is in domain [0, 10].
• Output luminance $Y$ is in domain [0, 100].

References

• http://www.scribd.com/doc/89648322/ASTM-D1535-08e1-Standard-Practice-for-Specifying-Color-by-the-Munsell-System

Examples

>>> luminance_ASTM_D1535_08(3.74629715382)  
10.1488096...

colour.colorimetry.luminance.LUMINANCE_METHODS = CaseInsensitiveMapping({u'astm2008': <function luminance_ASTM_D1535_08 at 0x102e0f668>, u'Newhall 1943': <function luminance_newhall1943 at 0x102e0f578>, u'ASTM D1535-08': <function luminance_ASTM_D1535_08 at 0x102e0f668>, u'CIE 1976': <function luminance_1976 at 0x102e0f5f0>, u'cie1976': <function luminance_1976 at 0x102e0f5f0>})¶

Supported luminance computations methods.

LUMINANCE_METHODS : dict

(‘Newhall 1943’, ‘CIE 1976’, ‘ASTM D1535-08’)

Aliases:

• ‘cie1976’: ‘CIE 1976’
• ‘astm2008’: ‘ASTM D1535-08’

colour.colorimetry.luminance.luminance(LV, method=u'CIE 1976', **kwargs)[source]¶

Returns the luminance $Y$ of given Lightness $L^*$ or given Munsell value $V$.

Parameters:	LV (numeric) – Lightness $L^*$ or Munsell value $V$. method (unicode, optional) – (‘Newhall 1943’, ‘CIE 1976’, ‘ASTM D1535-08’) Computation method. **kwargs (**) – Keywords arguments.
Returns:	luminance $Y$.
Return type:	numeric

Notes

• Input LV is in domain [0, 100] or [0, 10] and optional luminance $Y_n$ is in domain [0, 100].
• Output luminance $Y$ is in domain [0, 100].

Examples

>>> luminance(37.9856290977)  
10.0800000...
>>> luminance(37.9856290977, Yn=100)  
10.0800000...
>>> luminance(37.9856290977, Yn=95)  
9.5760000...
>>> luminance(3.74629715382, method='Newhall 1943')  
10.4089874...
>>> luminance(3.74629715382, method='ASTM D1535-08')  
10.1488096...