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. [2]_

  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. [3]

References

[3]	(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:978-0471399186

colour.constants.cie.KP_M = 1700¶

Rounded maximum scotopic luminous efficiency $K^{\prime}_m$ value in $lm\cdot W^{-1}$.

KP_M : numeric

Notes

• To be adequate for all practical applications the $K^{\prime}_m$ value has been rounded from the original 1700.06 value. [3]