Study of various metrics evaluating color quality of light sources

Abstract

CIE (Commission Internationale del Eclairage) color rendering index (CRI) is the only internationally recognized and widely used metric to assess color rendering abilities of light sources. Despite its simplicity, CIE CRI has many shortcomings. These include outdated color space and outdated chromatic adaptation formula. CIE established technical committees several times to tackle the problems with CIE CRI. However, every committee was closed in five to ten years as they could not find a solution that every member would agree upon. One such committee formed by CIE in 2006 is CIE TC 1-69 (Color Rendition by White Light Sources). The aim of CIE TC 1-69 is to recommend new assessment procedures for assessing the color rendition properties of white-light source used for illumination. A wide variety of approaches have been proposed. Till now nine metrics have been submitted to CIE TC 1-69. Some of the proposed metrics address specific aspect of color rendition while other metrics try to intregate more than one aspects of color rendition. CIE is in the process of developing and recommending a new final metric. This work provides walk-through of various metrics to evaluate color quality of light sources. Altogether fourteen different metrics are discussed. This work also discusses how the new metrics will solve the limitations of CIE CRI.