Five major changes in the new color quality assessment method released by IES

Figure: Members of the IES Color Quality Working Group who proposed the TM-30-15 color evaluation system

The document was approved after review by the IES Color Council, the Technical Review Board and the Board of Directors.

Compared to the existing CIE color rendering index CRI, this new evaluation method of IES has the following five major changes:

1, double indicators : evaluation of light source color is no longer just using one indicator, but by two indicators - Rf and Rg.

Rf is used to characterize the degree of similarity of each standard color compared to the reference source under the illumination of the test source (100 represents exactly the same; 0 represents a large difference).

Rg represents the change of saturation of each standard color under the test light source compared with the reference light source (100 represents the same saturation, greater than 100 means the light source can increase the saturation of the color, and below 100 means the saturation of the color under the test light source. Lower).

Figure: Color fidelity Rf and color saturation Rg

Figure: Color fidelity index Rf

Figure: Color saturation index Rg

2. Standard color: Compared with CRI, there are only 8 standard colors. The new system uses 99 standard colors. These 99 standard colors are no longer Monser color cards, but are carefully selected from the colors of 105,000 objects. They represent the common colors that can be seen in life (from saturation to unsaturated, from light to dark), and the 99 standard colors are equally sensitive to wavelengths (it is difficult to increase the index by spectral gaming).

Figure: 8 standard colors R1-R8 used by CRI

Figure: The IES TM-30-15 uses 99 standard colors and is carefully selected from the colors of 105,000 objects, representing the common colors that can be seen in life (from saturated to unsaturated, from bright to dark).

Figure: Spectral reflection distribution curve of 99 standard colors in the new IES standard

3. Reference light source: There is a 5000K catastrophe problem due to the reference light source used by CRI (ie blackbody radiation when 5000K is used; natural light model is higher than 5000K). This new system uses blackbody in the range of 4500K-5500K. The spectrum of the radiation mixed with the natural light model serves as a reference source. In addition, both Rf and Rg use the same reference light source color temperature as the source to be tested, thereby overcoming an important drawback of GAI.

4. Colorimetry: The system uses a more uniform chromaticity space, color adaptive equation and color appearance model (CIE Color Appearance Model 02).

5. Color distortion icon: Since the two indicators can only comprehensively evaluate the average color rendering ability of the light source for various colors, it is sometimes important for the color rendering ability of certain colors (especially for lighting designers). The new method also provides a color distortion icon while providing dual indicators to provide more intuitive information to indicate color drift and saturation changes for various colors.

Figure: Color distortion icons that can be more intuitively represented for color drift and saturation changes of various colors