Colorimetric equipment is similar to that used in spectrophotometry. Some related equipment is also mentioned for completeness. • A
tristimulus colorimeter measures the tristimulus values of a color. • A
spectroradiometer measures the absolute spectral
radiance (intensity) or
irradiance of a light source. • A
spectrophotometer measures the spectral
reflectance,
transmittance, or relative irradiance of a color sample. • A
spectrocolorimeter is a spectrophotometer that can
calculate tristimulus values. • A
densitometer measures the degree of light passing through or reflected by a subject. On the other hand, tristimulus colorimeters are purpose-built, cheaper, and easier to use. The
CIE (International Commission on Illumination) recommends using measurement intervals under 5 nm, even for smooth spectra. Internally the meter is typically a
silicon photodiode tristimulus colorimeter. The
correlated color temperature can be calculated from the tristimulus values by first calculating the
chromaticity co-ordinates in the
CIE 1960 color space, then finding the closest point on the
Planckian locus. == See also ==