Tristimulus colorimeter

It takes a limited number of wideband spectral energy readings along the visible spectrum by using filtered photodetectors; e.g. silicon photodiodes.

[1] A colorimeter with the known value of absolute error allows measuring (x,y)-chromaticity coordinates in red, green, blue and white colors.

[2] Originally, three glass filters whose transmittance spectra mimicked the CIE color matching functions (shown below) were employed.

[4] A camera or colorimeter is said to be colorimetric if it satisfies the Luther condition [de] by Robert Luther [de] (1868–1945) (also called the "Maxwell–Ives criterion"),[5] reducing observer metamerism color errors, if the product of the spectral responsivity of the photoreceptor and the spectral transmittance of the filters is a linear combination of the CMFs.

[6] A colorimeter or a digital camera with a color filter array can, under certain conditions, be used as an alternative to a spectrophotometer.