Revolutionizing Color Rendition Assessment: Introducing TM-30-15

In the lighting world, there is a well-known metric called CRI, which stands for Color Rendering Index. It quantitatively measures how accurately a light source can depict the colors of objects compared to an ideal or natural light source. A higher CRI value indicates a more faithful representation of colors.

However, the predictive ability of CIE Ra (similar to CRI) in determining color appearance has been criticized in favor of measures based on color appearance models like CIECAM02 and the CIE metamerism index for daylight simulators. CRI is unsuitable for visually assessing light sources, particularly those below 5000 kelvin (K). New standards, such as IES TM-30, have emerged to address these concerns and are replacing CRI among professional lighting designers. However, CRI remains common in household lighting products.

TM30-15 consists of three main components:

1. Rf: Similar to CIE Ra (CRI), it characterizes the average color shift of the 99 color evaluation samples (CES) to determine the similarity between the test source and reference illuminant. Rf values range from 0 to 100.
2. Rg: This component compares the area enclosed by the average chromaticity coordinates in 16 hue bins, indicating the average saturation level of the test source relative to the reference illuminant. A score of 100 represents neutrality, values above 100 indicate increased saturation and values below 100 indicate decreased saturation. The range of values expands as fidelity decreases.
3. A graphical representation of Rg visually displays which colors are affected by the light source, appearing washed out or more vivid. This graphical representation includes the Color Vector Graphic and the Color Saturation Graphic. The Color Vector Graphic illustrates hue and saturation changes in each hue bin compared to the reference, providing an understanding of how different hues are rendered. The Color Saturation Graphic offers a simplified visual representation of saturation changes based on average performance in each hue bin.

Let’s compare CRI and TM30-15:

	CIE 13.3-1995 (CRI)	IES TM-30-15
Year of Issuance	1965, 1974 (Revision), 1995	2015
Color Space	CIE 1964 UVW*	CAM02-UCS (CIECAM02)
Number of Color Samples	Eight general (for Ra) plus six special (for Ris)	99
Color Volume Coverage	Limited	Full and equal
Saturated Samples	No	Yes
Sample Types	Munsell samples only (limited pigments)	Variety of real objects
Sample Spectral Uniformity	No	Yes
Reference Illuminants	Blackbody radiation, CIE D series	Blackbody radiation, CIE D series
Reference Transition	Sharp at 5000 K	Blended between 4500 K and 5500 K
Output Measures	General index, Ra (fidelity) Six particular indices, Ri (fidelity)	Fidelity Index, Rf Gamut Index, Rg Color Vector/Saturation Graphics 16 hue-based fidelity indices 16 hue-based chroma indices One skin-specific fidelity index 99 individual fidelity values
Score Ranges	Max 100 with no lower limit, variable scaling	0 to 100, consistent scaling

Why is TM30-15 important?

• CRI is currently widely used and is not going away soon. AFTER CONSIDERING THE INPUT RECEIVED, the IES are still awaiting feedback and will likely transition to TM30-15.
• TM30-15 is expected to be employed selectively, especially in applications where color rendering is a significant concern, such as specifier choices and retail shops.
• About TM30-15, it is possible to manipulate CRI scores by focusing on only the nine colors it evaluates. This allows manufacturers to inflate their scores without improving the overall quality of the light source.

For specifiers:

• TM-30-15 is an approved method, and using it while providing feedback can contribute to its further development and refinement.
• Selecting a “better” light source may pose more challenges but can also yield more rewarding results.

The following visuals demonstrate the changes that occur when altering various metrics such as Rf, Rg, and CRI, including comparisons of color vector graphs.

Additional Resources

MyLikeLed is a professional LED light strip manufacturer; we produce high-quality LED light strips and LED Neon Flex. You and check the below resources to understand TM-30-15 better.

Evaluating Color Rendition Using IES TM-30-15

Understanding and Applying TM-30-15

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