Recently, the International Commission on Illumination (CIE) released the CIE 2017 Color Fidelity Index for Accurate Scientific Use.
The CIE Color Rendering Index (CRI), in particular the general color rendering index, Ra, is widely adopted and used by the lighting industry. However, limitations of the CRI have been recently addressed, especially for solid-state light sources. This mismatch arises, first, from inaccuracies of the CRI in its intended role as a color fidelity index; and second, from perception-related color quality effects beyond color fidelity.
Therefore, the CIE determined that, better color quality characterization methods are needed to measure and specify white-light sources, and the work was divided into two corresponding tasks: (1) to develop a scientifically accurate color fidelity index, assigned to TC 1-90, and (2) to develop one or more perception-related color quality measures beyond fidelity, assigned to TC 1-91 for initial work.
This Technical Report CIE 224, developed by TC 1-90, is a research report describing a general color fidelity index, Rf, as a scientifically accurate measure of color fidelity. This color fidelity index is based on the fidelity index of the Illuminating Engineering Society of North America, defined in TM-30-15. It addresses several previously reported inaccuracies of the CRI as a color fidelity measure.
The Rf represents how closely the color appearances of the entire sample set are reproduced (rendered) on average by a test light as compared to those under a reference illuminant. Thus, similar to the Ra, the Rf combines the computed color differences for all test-color samples in one single average index value, and is only one aspect of color quality not considering perception/preference effects. Therefore, it is not a replacement of the Ra. Replacement of the CRI will be a matter of future study and discussion that will include the Rf, along with development of a set of new color quality measures for assessing perception-related effects.