LEDs are light- and near-infrared emitting diodes. Their line-like emission spectra causes considerable difficulties, not unlike phosphor emission of color CTRs, when accurate color measurement is required. LEDs exhibit many different spatial distribution characteristics as well, requiring relatively large area, uniform detector surface for photometric and colorimetric evaluation. Discussion of several diffferent type of colorimeters follows, showing trade-off between precision and price as well as suitability in their application for many different situations.
Kathleen Muray, Kathleen Muray,
"Color measurement of LEDs (diode emitters) with tristimulus colorimeter", Proc. SPIE 2550, Photodetectors and Power Meters II, (26 September 1995); doi: 10.1117/12.221414; https://doi.org/10.1117/12.221414