TM-30-15 describes a calculation method to evaluate color rendition properties of light sources. The outcomes are summarized as fidelity index, gamut index and additional graphics and indices. The method can provide very valuable findings for designers. Here we give some answers on how can we better communicate outcomes of such evaluations. Especially the chroma change by hue indices and the hue fidelity indices contain information that are highly relevant to designer, interior architects and all concerned to select colors for the built environment.


The TM-30-15 provides output data for 16 hue bins. The numbering of the bins is counterclockwise. To ease communication the position of the four unique hues (yellow, red, blue, green) was added to the graphic representation (middle and left graphic). Additionally the bins were renamed to follow a clockwise order.


The chroma change by hue indices provides numerical values for relative chroma change in each of 16 hue bins, which can be used to evaluate saturation (positive values) or desaturation (negative values) of yellows, reds, blues, greens, and in-between hues compared to the reference.


Hue fidelity indices provides numerical characterization of color fidelity in each of 16 hue bins, which can be used to evaluate how similarly the test source renders yellows, reds, blues, greens, or in-between hues compared to the reference. Values range from 0 to 100. Specific values may be used to supplement average values if one hue type is of particular concern. These scores are analogous to the special indices of the CRI system (e.g., R9), but are more robust because they combine several samples with different spectral features.

Graphics above show results from a LED RGBAC light source with a CCT of 3600K. Here is a one page summary for download

  LED RGBA 3600K lr (76.3 KiB)

This summary introduces you to two graphical representations intended to provide quick understanding of how certain hues are rendered.

  Graphics to ease communication (655.8 KiB)

Here are examples of color vector graphics for some light sources.

Additional links to IES TM-30-15 resources:

Some material in german

Links to additional information and resources about IES TM-30-15


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