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: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. [2]