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Second, numerous “marketing strategies” exist to exploit this scale.

Example: a 4100K CCT light source is measured against a 2700K perfect source (acceptable
under CRI measurement criteria). The warmer 2700K perfect source, even though it has a CRI of
100, is weaker in intensity on the blue end of the visible spectrum while the 4100K test source is
emitting more intensity there. This renders a higher CRI than if it were compared to the 5000K
daylight spectrum despite the fact it is the closer perfect source.

Color Quality Scale (CQS)

The CQS is a more modern approach to color measurement. The National Institute of Standards and
Technology (NIST), charged with the development of the CQS, states that the colors referenced by the
(4)
CRI “do not adequately span the range of normal object colors” .

Figure 6. Colors of the Color Quality Scale

The samples of the CQS span the entire visible spectrum in evenly spaced wavelengths and provide for
color saturation not addressed by the CRI.

While the CIE has tested and concluded that the CQS is a more effective scale for the measurement of
color rendition, it has yet to be implemented. Whether this is due to more development being required
or the influence of incumbent lighting manufacturers protecting decades of work in tuning their
phosphors is a subject beyond the scope of this document. Regardless, while the CQS continues in the
basic vein of the CRI, it still does not encompass the roughly ten million colors the human eye discerns.

Figure 5. Laying CQS Over Fluorescent and SSL

Presently, the CRI is the only reported standard. While the two light sources above are similar in CRI, it’s
easy to see how this index misrepresents the truth in color rendition. When crossing technologies, the
solution to the inadequacy of the CRI is personal interpretation of the spectral distributions; this
becomes easy when comparing the obvious differences between fluorescent and SSL sources.

Competitive Analysis, Color Rendering in White Light Page 5