A few definitions...

	Spectrophotometer A device to measure the spectral energy distribution. It can therefore also provide the CIE xyz tristimulus values. Illuminant C A standard for white light that approximates sunlight. It is defined by a color temperature of 6774 K. Complementary colors Colors which can be mixed together to yield white light. For example, colors on segment CD are complementary to the colors on segment CB. Dominant wavelength The spectral color which can be mixed with white light in order to reproduce the desired color. color B in the above figure is the dominant wavelength for color A. Non-spectral colors Colors not having a dominant wavelength. For example, color E in the above figure. Perceptually uniform color space A color space in which the distance between two colors is always proportional to the perceived distance. The CIE XYZ color space and the CIE chromaticity diagram are not perceptually uniform, as the following figure illustrates. The CIE LUV color space is designed with perceptual uniformity in mind.