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The 1932 CIE chromaticity diagram is one way to objectively describe color. The three components of human color perception (red, green, and blue) can be transformed to another three dimensional space where one axis is radiance/luminance independent of chromaticity and the other two axes describe the chromaticity. The 1932 diagram uses x and y coordinates to represent the chromaticity, thus the term xy chromaticity is used to specify the axes. The colored boundary line represents the coordinates of intense monochromatic light, such as that from lasers. White light is used as a reference point. In the SpectraWiz software, this diagram is used in conjunction with radiometry measurements (using any of the five radiometry units). It can be found under “Applications” > “CIE Color Measurement,” under “Color,” or by clicking the rainbow icon on the right of the toolbar. A yellow line connects the color point to the white reference point.

Thinking in polar coordinates with white light at the origin provides a more intuitive interpretation. The angle describes the dominant wavelength and the length describes the purity.