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_ASTMD153508(): luminance $Y$ computation of given Munsell value $V$ using ASTM D1535-08e1 (2008) method.
• luminance_1976(): luminance $Y$ computation of given Lightness $L^*$ as per CIE Lab implementation.

colour.colorimetry.luminance.luminance_Newhall1943(V, **kwargs)[source]¶

Returns the luminance $R_Y$ of given Munsell value $V$ using Sidney M. Newhall, Dorothy Nickerson, and Deane B. Judd (1943) method.

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

Notes

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

References

[1]	Newhall, S. M., Nickerson, D., & Judd, D. B. (1943). Final report of the OSA subcommittee on the spacing of the munsell colors. JOSA, 33(7), 385. doi:10.1364/JOSA.33.000385

Examples

>>> luminance_Newhall1943(3.74629715382)  
10.4089874...

colour.colorimetry.luminance.luminance_ASTMD153508(V, **kwargs)[source]¶

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

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

Notes

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

References

[4]	ASTM International. (n.d.). ASTM D1535-08e1 Standard Practice for Specifying Color by the Munsell System. doi:10.1520/D1535-08E01

Examples

>>> luminance_ASTMD153508(3.74629715382)  
10.1488096...

colour.colorimetry.luminance.luminance_1976(Lstar, Y_n=100)[source]¶

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

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

Notes

• Input Lightness $L^*$ and reference white luminance $Y_n$ are in domain [0, 100].
• Output luminance $Y$ is in domain [0, 100].

References

[2]	Wyszecki, G., & Stiles, W. S. (2000). CIE 1976 (L*u*v*)-Space and Color-Difference Formula. In Color Science: Concepts and Methods, Quantitative Data and Formulae (p. 167). Wiley. ISBN:978-0471399186

[3]	Lindbloom, B. (2003). A Continuity Study of the CIE L* Function. Retrieved February 24, 2014, from http://brucelindbloom.com/LContinuity.html

Examples

>>> luminance_1976(37.9856290977)  
array(10.0800000...)
>>> luminance_1976(37.9856290977, 95)  
array(9.5760000...)

colour.colorimetry.luminance.LUMINANCE_METHODS = CaseInsensitiveMapping({u'astm2008': <function luminance_ASTMD153508 at 0x2abef8de82a8>, u'Newhall 1943': <function luminance_Newhall1943 at 0x2abef8de8140>, u'ASTM D1535-08': <function luminance_ASTMD153508 at 0x2abef8de82a8>, u'CIE 1976': <function luminance_1976 at 0x2abef8de8320>, u'cie1976': <function luminance_1976 at 0x2abef8de8320>})¶

Supported luminance computations methods.

LUMINANCE_METHODS : CaseInsensitiveMapping

{‘Newhall 1943’, ‘ASTM D1535-08’, ‘CIE 1976’}

Aliases:

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

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

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