Color quality scale (CQS) is a

color rendering The color rendering of a light source refers to its ability to reveal the colors of various objects faithfully (i.e. to produce Metamerism (color), illuminant metamerism) in comparison with an ideal or natural light source. Light sources with good ...

score – a quantitative measure of the ability of a

light source Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

to reproduce

color Color (or colour in English in the Commonwealth of Nations, Commonwealth English; American and British English spelling differences#-our, -or, see spelling differences) is the visual perception based on the electromagnetic spectrum. Though co ...

s of illuminated objects. Developed by researchers at

NIST The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical s ...

the metric aims to overcome some of the issues inherent in the widely used color rendering index (CIE Ra, 1974). * The color space used in CIE R_a ( CRI) is outdated and nonuniform, and CQS uses

CIELAB The CIELAB color space, also referred to as ''L*a*b*'', is a color space defined by the International Commission on Illumination (abbreviated CIE) in 1976. It expresses color as three values: ''L*'' for perceptual lightness and ''a*'' and ''b* ...

as a replacement. * The Von Kries chromatic adaptation transform used by R_a does not perform as well as other available models. CQS uses CMCCAT2000. * CIE R_a is based on desaturated samples, and a lamp's performance in rendering these samples faithfully is not necessarily linked to how it may perform with samples of higher saturation. CQS uses higher saturation samples. * ‘Pure’ fidelity (where all deviations are considered bad) does not account for desired chromaticity changes. Increased saturation might be preferred. CQS does not penalise against increases in saturation. * In CIE R_a the arithmetic mean is taken of the color differences for the individual samples. In CQS the individual results are combined through a

root mean square In mathematics, the root mean square (abbrev. RMS, or rms) of a set of values is the square root of the set's mean square. Given a set x_i, its RMS is denoted as either x_\mathrm or \mathrm_x. The RMS is also known as the quadratic mean (denote ...

instead, so that a small number of poorly rendered objects reflects with greater strength in the overall result. * Negative values of CQS are made impossible due to their potential for consumer confusion. * CCTs of lower than 2800K are penalised so that the CQS is more representative of their actual color rendering as opposed to their fidelity. The CQS generates the general index Q_a. Several manufacturers are beginning to publish data on CQS scores of their products, including some who claim light sources with CQS scores up to 97.High CRI LED Lighting Supplier
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References

Lighting Color scales {{Color-stub

See also

References