class colour.quality.CQS_Specification[source]

Defines the Colour Quality Scale (CQS) colour quality specification.

  • name (unicode) – Name of the test spectral distribution.
  • Q_a (numeric) – Colour quality scale \(Q_a\).
  • Q_f (numeric) – Colour fidelity scale \(Q_f\) intended to evaluate the fidelity of object colour appearances (compared to the reference illuminant of the same correlated colour temperature and illuminance).
  • Q_p (numeric) – Colour preference scale \(Q_p\) similar to colour quality scale \(Q_a\) but placing additional weight on preference of object colour appearance, set to None in NIST CQS 9.0 method. This metric is based on the notion that increases in chroma are generally preferred and should be rewarded.
  • Q_g (numeric) – Gamut area scale \(Q_g\) representing the relative gamut formed by the (\(a^*\), \(b^*\)) coordinates of the 15 samples illuminated by the test light source in the CIE L*a*b* object colourspace.
  • Q_d (numeric) – Relative gamut area scale \(Q_d\), set to None in NIST CQS 9.0 method.
  • Q_as (dict) – Individual Colour Quality Scale (CQS) data for each sample.
  • colorimetry_data (tuple) – Colorimetry data for the test and reference computations.


[DO10], [OD08], [OD13]

Create new instance of CQS_Specification(name, Q_a, Q_f, Q_p, Q_g, Q_d, Q_as, colorimetry_data)


Initialize self. See help(type(self)) for accurate signature.


count Return number of occurrences of value.
index Return first index of value.


Q_a Alias for field number 1
Q_as Alias for field number 6
Q_d Alias for field number 5
Q_f Alias for field number 2
Q_g Alias for field number 4
Q_p Alias for field number 3
colorimetry_data Alias for field number 7
name Alias for field number 0