What does CQS mean ?

CQS : color quality Scale

CQS is a method used to evaluate the color quality of a light source. It comprehensively considers the color nature of the light source, including color saturation, color temperature, color consistency and other factors, through a comprehensive score to judge the comprehensive quality of the light source.

The indicator was developed by researchers at NIST. Because the CRI proposed by the International Commission on Lighting has caused some problems with the use of unsaturated colors and a small amount of sample colors, CQS uses higher saturation colors and proposes 15 new colors to evaluate the light source, with 100 representing the best light source quality and 0 representing the worst light source quality. To calculate CQS, we also need to introduce the concepts of Rf and Rg.

Fidelity Rf is used to represent the Color Rendering Index (CRI) of the light source, that is, the similarity of each standard color under the exposure of the test light source and under the exposure of the reference light source. The number ranges from 0 to 100, and the higher the value, the better the color authenticity.

The formula for calculating Rf is Rf=Ra*Rw*Rv. Among them, Ra is the chromatic index, representing the ability to reproduce black, white and gray; Rw is the color index, representing the ability of the light source to reproduce color. Rv is the color temperature consistency index, representing the color consistency of the light source at different color temperatures.

Rf =100 is the maximum value, which means no color difference with the color under the natural light source, and the color effect is realistic

Rf = 0 is the minimum value, representing the largest color difference with the natural light source, and the color effect is distorted

Color saturation Rg is used to represent the color Gamut Index GAI (Gamut Area Index) of the light source, that is, the saturation degree of each standard color under the irradiation of the test light source compared with the reference light source, and the index 100 represents the best saturation.

The formula for calculating Rg is Rg=R9*R12*Rf '. Among them, R9 is the saturation red index, representing the ability of the light source to reproduce saturated red. R12 is the saturation blue index, which represents the ability of the light source to reproduce saturated blue. Rf 'is the product of the remaining six color indices, representing the ability to reproduce colors other than saturated red and blue.

Rg =100, which means that the saturation of the light source is the same as that of natural light, and the color saturation is moderate

Rg>100, which means that the light source can increase the saturation of the color, and the object looks more vivid and dynamic

Rg<100, which means that the saturation of the color will be reduced under the test light source, and the color saturation will be insufficient, and the object will become gray and dull

CQS is calculated as follows: CQS=Rf*Rg. Among them, Rf is the fidelity, also known as the color reproduction index, representing the ability of the light source to reproduce the color of the object. Rg is the saturation retention index, which represents the ability of the light source to maintain color saturation. Therefore, the color quality of the light source can be evaluated quantitatively by CQS calculation formula.