A New Era for Evaluating Color Rendition
[ This post originally appeared in the Minnesota Electrical Association’s July 2016 newsletter. ]
Color rendering is an important consideration in almost all lighting projects. For the past 50 years the general color rendering index (CRI) has been the industry standard for selecting appropriate lighting for a given space. Due to its greater spectral capability, the advancement of solid-state lighting has started to expose the limitations of this standard. To address these limitations, the Illuminating Engineering Society (IES) Color Committee has developed a new system called IES TM-30-15 (TM-30).
Like the CRI, TM-30 is still a referenced-based system, but this is where the similarities begin to diverge. At the foundation of the TM-30 are 99 color evaluation samples as opposed to the eight samples used in the CRI. This allows practitioners to better estimate how a luminaire will perform in specific applications. TM-30 also uses a more uniform color space, which creates more accuracy in calculating color difference.
Although there are many technical differences between TM-30 and the CRI, the additional information TM-30 provides will be the most important aspect for most practitioners. TM-30 generates eight different outputs that range from higher level averages to specific values to graphical representations. Two principle parameters, the Fidelity Index (Rf ) and Gamut Index (Rg), not only characterize the conformity of a product to the reference source, but also provide information on which colors are most distorted. The information provided by the relationship of Rf and Rg may be enough for most lighting projects, but TM-30 allows practitioners to take a much deeper dive if necessary. TM-30 is currently a voluntary standard. For more information, please go to: energy.gov/eere/ssl/downloads/evaluating-color-rendition-using-ies-tm-30-15
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