Color Rendering Index. A measure of a light source to illuminate objects as faithfully as possible compared to natural daylight or the "ideal" source. Higher numbers are better: a CRI of 100 is "perfect"--the common incandescent/halogen source. Most fluorescents fall into the 50-75 range. The orange sodium-vapor streetlights, which make everything appear unnatural, have a CRI of 5-25. More information at http://www.lrc.rpi.edu/programs/nlpip/lightinganswers/lightsources/whatisColorRenderingIndex.asp. See also Learn About Light: Color Rendering: GE Commercial Lighting Products.