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Colorimetry is "the science and technology used to quantify and describe physically the human color perception". [1] It is similar to spectrophotometry, but is distinguished by its interest in reducing spectra to the physical correlates of color perception, most often the CIE 1931 XYZ color space tristimulus values and related quantities.
In ultraviolet (UV) methods there is no visible color change but the principle is exactly the same, i.e. the measurement of a change in the absorbance of the solution. UV methods usually measure the difference in absorbance at 340 nm wavelength between nicotinamide adenine dinucleotide (NAD) and its reduced form (NADH).
Colorimetric assays use reagents that undergo a measurable color change in the presence of the analyte. They are widely used in biochemistry to test for the presence of enzymes, specific compounds, antibodies, hormones and many more analytes. For example, para-Nitrophenylphosphate is converted into a yellow product by alkaline phosphatase enzyme.
These color spaces are fundamental tools for measuring color for industry, including inks, dyes, and paints, illumination, color imaging, etc. The CIE color spaces contributed to the development of color television, the creation of instruments for maintaining consistent color in manufacturing processes, and other methods of color management.
In colorimetry, the Munsell color system is a color space that specifies colors based on three properties of color: hue (basic color), value , and chroma (color intensity). It was created by Albert H. Munsell in the first decade of the 20th century and adopted by the United States Department of Agriculture (USDA) as the official color system ...
A colorimeter or a digital camera with a color filter array can, under certain conditions, be used as an alternative to a spectrophotometer. [7] [8] The illuminant and observer conditions should be specified when citing a measurement (e.g. D65/10°). [9] The quality of a colorimeter may be assessed using the means in CIE publication 179:2007. [10]
The Standard Reference Method or SRM [1] is one of several systems modern brewers use to specify beer color. Determination of the SRM value involves measuring the attenuation of light of a particular wavelength (430 nm) in passing through 1 cm of the beer, expressing the attenuation as an absorption and scaling the absorption by a constant (12.7 for SRM; 25 for EBC).
This method has successfully been demonstrated in forensic soil analysis, using the Munsell colour system. [4] A similar method has been applied to nuclear forensics, for the quantification of uranium oxide powder color. [5] Both methods report suitability for use by both experts and non-experts alike, as the methods only require a camera on site.