A tristimulus colorimeter, colloquially shortened to ''colorimeter'', is used in

digital imaging Digital imaging or digital image acquisition is the creation of a digital representation of the visual characteristics of an object, such as a physical scene or the interior structure of an object. The term is often assumed to imply or include t ...

to profile and calibrate output devices. It takes a limited number of wideband spectral energy readings along the

visible spectrum The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called '' visible light'' or simply light. A typical human eye will respond to ...

by using filtered

photodetector Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation. There is a wide variety of photodetectors which may be classified by mechanism of detection, such as photoelectric or photochemical effects, or ...

s; e.g. silicon photodiodes. A colorimeter with the known value of absolute error allows measuring (x,y)-chromaticity coordinates in red, green, blue and white colors. Measured values are used for calculation of LCD profile coefficients. Originally, three glass filters whose

transmittance Transmittance of the surface of a material is its effectiveness in transmitting radiant energy. It is the fraction of incident electromagnetic power that is transmitted through a sample, in contrast to the transmission coefficient, which is t ...

spectra mimicked the CIE

color matching function The CIE 1931 color spaces are the first defined quantitative links between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color vision. The mathematical relationships that defin ...

s (shown below) were employed. A

filter bank In signal processing, a filter bank (or filterbank) is an array of bandpass filters that separates the input signal into multiple components, each one carrying a single frequency sub-band of the original signal. One application of a filter bank is ...

may be used to decompose the individual color matching functions if more accuracy is desired. A camera or colorimeter is said to be ''colorimetric'' if it satisfies the by (1868–1945) (also called the "

Maxwell Maxwell may refer to: People * Maxwell (surname), including a list of people and fictional characters with the name ** James Clerk Maxwell, mathematician and physicist * Justice Maxwell (disambiguation) * Maxwell baronets, in the Baronetage of ...

– Ives criterion"), 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. A colorimeter or a digital camera with a

color filter array In digital imaging, a color filter array (CFA), or color filter mosaic (CFM), is a mosaic of tiny color filters placed over the pixel sensors of an image sensor to capture color information. The term is also used in reference to e paper devices ...

can, under certain conditions, be used as an alternative to a spectrophotometer. The

illuminant A standard illuminant is a theoretical source of visible light with a spectral power distribution that is published. Standard illuminants provide a basis for comparing images or colors recorded under different lighting. CIE illuminants The Inter ...

and observer conditions should be specified when citing a measurement (e.g. D65/10°). The quality of a colorimeter may be assessed using the means in CIE publication 179:2007. There are various calibration methods for tristimulus colorimeters. File:Spyder4Elite color sensor.JPG, Color sensor of a colorimeter File:CIE 1931 XYZ Color Matching Functions.svg, The

CIE 1931 The CIE 1931 color spaces are the first defined quantitative links between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color vision. The mathematical relationships that defin ...

XYZ color matching functions

References

{{reflist Color Spectrometers Laboratory equipment