IES TM-30-15


IES Method for Evaluating Light Source Color Rendition
standard by Illuminating Engineering Society, 2015


This evaluation method is applicable to light sources and lighting systems intended for general illumination of indoor spaces and some outdoor settings, at light levels where photopic vision is dominant. It is best suited to characterize nominally white light sources (i.e., those that fall on or near the Planckian locus).

This Technical Memorandum describes a method for evaluating light source color rendition that takes an objective and statistical approach, quantifying the fidelity (closeness to a reference) and gamut (increase or decrease in chroma) of a light source. Importantly, it does not attempt to evaluate human color preference or provide a single number that captures the combined color rendition qualities. However, using the two-dimensional characterizationprovided by the Fidelity Index (Rf) and Gamut Index (Rg), a user is expected to be able to rely on experience and/or design guidelines to determine what is most appropriate for the specific application in consideration. The method also generates a color vector graphic that indicates average hue and chroma shifts, and which helps with interpreting the values of Rf and Rg.

NOTE: See the table of contents page of TM-30-15 for the URL address where the Excel calculation tool for the standard may be downloaded.

Includes Errata 1

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