Color rendering: Beyond pride and prejudice

It is a truth, universally ignored, that a single metric of color rendering must be in want of another. Evidence presented here, together with those from an earlier study, strongly suggest that the quest for a single metric to quantify color rendering will be in vain. Rather, the strengths of color rendering index (CRI) and of gamut area index (GAI) seem to counteract the weaknesses of one another, such that together they can be used to guide lighting practitioners in choosing a source that will provide good color rendering of most objects in most applications. The present study was conducted to determine whether sources, both warm and cool, with high levels of both CRI (above 80) and GAI (above 80 and less than 100) were judged better than ones with high levels of just CRI or just GAI. The results support the conclusion that a two-metric system of color rendering is needed for general illumination applications.