Color Fidelity Index (Rf) is a scientific indicator used to quantify the ability of a light source to restore the color of an object. It aims to more accurately reflect the color rendering performance of the light source in real scenes.
Basic concept
The color fidelity index Rf was proposed by the International Commission on Illumination (CIE) in the technical report CIE 224:2017. It is defined as: the average value of the color reproduction degree of 99 standard color samples compared with the reference light source (daylight or Planck radiation) of the same color temperature. The Rf value range is 0-100. The closer the value is to 100, the more realistic the color reproduction is.
Difference from traditional color rendering index (CRI/Ra)
Sample size expansion: CRI uses only 8 medium-saturation color samples (R1-R8), while Rf is based on 99 color samples, covering a wider color gamut and spectral characteristics (including high-saturation colors);
Color difference calculation optimization: CAM02-UCS uniform color space (based on the three-dimensional color model perceived by the human eye) is used to replace the two-dimensional color difference formula of CRI, significantly improving the calculation accuracy;
Reference light source improvement: The definition of the color temperature transition zone (such as 4000K-5000K) is adjusted to make the comparison of light sources with different color temperatures more scientific