colour.constants.cie Module¶
CIE Constants¶
Defines CIE constants.

colour.constants.cie.
CIE_E
= 0.008856451679035631¶ CIE \(\epsilon\) constant.
CIE_E : numeric
Notes
The original CIE value for \(\epsilon\) is \(\epsilon=0.008856\), Lindbloom (2003) has shown that this value is causing a discontinuity at the junction point of the two functions grafted together to create the Lightness \(L^*\) function.
That discontinuity can be avoided by using the rational representation as follows: \(\epsilon=216\ /\ 24389\).
References
[1] Lindbloom, B. (2003). A Continuity Study of the CIE L* Function. Retrieved February 24, 2014, from http://brucelindbloom.com/LContinuity.html

colour.constants.cie.
CIE_K
= 903.2962962962963¶ CIE \(\kappa\) constant.
CIE_K : numeric
Notes
The original CIE value for \(\kappa\) is \(\kappa=903.3\), Lindbloom (2003) has shown that this value is causing a discontinuity at the junction point of the two functions grafted together to create the Lightness \(L^*\) function. [1]
That discontinuity can be avoided by using the rational representation as follows: \(k=24389\ /\ 27\).

colour.constants.cie.
K_M
= 683¶ Rounded maximum photopic luminous efficiency \(K_m\) value in \(lm\cdot W^{1}\).
K_M : numeric
Notes
 To be adequate for all practical applications the \(K_m\) value has been rounded from the original 683.002 value. [2]
References
[2] (1, 2) Wyszecki, G., & Stiles, W. S. (2000). Standard Photometric Observers. In Color Science: Concepts and Methods, Quantitative Data and Formulae (pp. 256–259,395). Wiley. ISBN:9780471399186