A reference source, such as blackbody radiation, is defined as having a CRI of 100. This is why [[incandescent lamp]]s have that rating, as they are, in effect, almost blackbody radiators.<ref>{{Cite web |title=Blackbody Radiator - an overview {{!}} ScienceDirect Topics |url=https://www.sciencedirect.com/topics/engineering/blackbody-radiator |access-date=2022-03-13 |website=www.sciencedirect.com}}</ref><ref>{{Cite web |last=Fixtures |first=Access |date=2017-01-26 |title=CRI: What Is the Color Rendering Index? Is It Accurate? |url=https://www.accessfixtures.com/color-rendering-index/ |access-date=2022-03-13 |website=Access Fixtures |language=en-US}}</ref> The best possible faithfulness to a reference is specified by CRI = 100, while the very poorest is specified by a CRI below zero. A high CRI by itself does not imply a good rendition of color, because the reference itself may have an imbalanced SPD if it has an extreme color temperature.
