Light sources with good color rendering are desirable in color-critical applications such as neonatal care[1] and art restoration.
Notable ones include: Researchers used daylight as the benchmark to which to compare color rendering of electric lights.
[3] To calculate a TLCI, a full measure of the spectral power distribution (SPD) of the light source is first taken.
Under the test and reference illuminant, an image of the ColorChecker is simulated using known reflectivities and the color curves of an average HDTV camera and display.
[10] The spectral similarity index (SSI) of 2016 is a scale that completely forgoes the comparison of color samples, instead directly comparing the SPDs of one light source to the reference.
The SSI is calculated by taking two integrated, normalized SPDs in the 5-nm intervals from 375 to 675 nm and finding a weighted relative difference between them.
Three reference design intents and priority levels are defined in TM-30 Annex E.[13] Before the aforementioned scales are devised to replace CRI, a number of other measures have been proposed.