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 ...
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 wav ...
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 by ...
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 th ...
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 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 o ...
– 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 can, under certain conditions, be used as an alternative to a spectrophotometer.
The illuminant 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.
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