A colorimeter is a light-sensitive instrument used in colorimetry for measuring the color intensity of an object or color sample in terms of the red, blue, and green components of light reflected from the object or sample. This is similar to the functioning of a human eye. The colorimeter works on the basis of Beer-Lambert’s law, which states that the absorption of light transmitted through a medium is directly proportional to the concentration of the medium.

When light passes through a homogenous medium, a part of the light is absorbed by the medium. As a result, there is a decrease in the intensity of the light emerging from the medium. A psychophysical analysis of the transmitted light based on human eye–brain perception is performed to obtain the color comparisons.

The sectrophotometer, color densitometer, and color photometer are the some important types of colorimeter. The spectrophotometer uses diffraction gratings to split the light spectrum to form a large number of bands. Color densitometers, mainly used in printing, only measure the color density of primary colors.

The manufacturing cost of a spectrophotometer is very high, which makes it very expensive. Further, it should be handled with utmost care and requires recalibration on a regular basis. Color photometers are also often expensive, but usually cost less than spectrophotometers.

Other types of colorimeter include digital, laboratory, and portable. The digital colorimeter uses light-emitting diodes (LEDs) as light sources for analyzing the absorption spectra and provides a liquid crystal display (LCD) of the analysis. Laboratory colorimeters are equipped with easy-to-use controls and are meant for educational purposes.

As the name suggests, a portable colorimeter is also easy to use and can be carried anywhere, irrespective of environmental conditions. This colorimeter can test a broad range of wavelengths and is ready to use under any condition. Portable colorimeters are used for studying water and soil properties.

Many colorimeters can be connected to a television or computer to analyze the color contrast and brightness adjustments for obtaining an optimized picture display on the screen. Colorimeters form a basic element of color management systems in the printing industry. Other industrial applications include checking the electronic components and quality of pulp paper and measuring the quality of printing ink.

Diamond merchants also utilize colorimeters to measure the optical properties of precious stones. The study of homogenous assays is one of the clinical applications of the colorimeter. In cosmetology, the colorimeter is used to measure the sun protection factor. In the digital imaging field, a CCD-based digital imaging tristimulus colorimeter has also been developed, which instantly measures the luminosity and chromaticity coordinates of different spatial locations.