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=WhatBlackbody IsRadiator Color- Rendering?an overview {{!}} ScienceDirect Topics |url=https://www.sciencedirect.com/topics/engineering/blackbody-radiator |access-date=2022-03-13 2. https://|website=www.accessfixturessciencedirect.com/color-rendering-index/}}</ref> <ref>{{Cite web |titlelast=BlackbodyFixtures Radiator|first=Access |date=2017-01-26 an|title=CRI: overviewWhat {{!}}Is ScienceDirectthe TopicsColor Rendering Index? Is It Accurate? |url=https://www.sciencedirectaccessfixtures.com/topicscolor-rendering-index/engineering/blackbody-radiator |access-date=2022-03-1013 |website=www.sciencedirect.comAccess 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.
