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The popularity of optical measurements in different fields of science, techniques, industry, agriculture, medicine is connected with the originality and volume of information about the content, properties and construction of substances, cells, materials, which can have optical radiations. Different fields of industry (metallurgy, machine building, chemistry, instruments making) widely use the methods of photometry (measurements of parameters of radiation in optical range) and radiometry for development and improvement of technologies, quality control of products etc.

Historically photometry occurred as science about visual light measurements, the value of which is determined by that important role, which plays the eyesight in human life. The increasing of accuracy of light measurements has a great effect not only on the development of the industry and scientific researches but also leads to significant saving taking into account the amount of electricity consumed for lightning.

One of the main directions of development of optical and physical measurements is colorimetry (measurement of color parameters). The necessity in this kind of measurements exists in such important branches of industry as polygraphic, textile, shoes, paint and varnish industry, paper, jewelry, automobile, petrochemical, and also in the cinema and on TV.

With the appearance of lasers the range of optical and physical measurements has been significantly expanded and it is impossible to imagine any branch where the results of precise optical and physical measurements are not actual. 

During the 16th CGPM in 1979 there was  approved the new determination of the basic SI units - candlepower unit: candela – candlepower in the given direction from the source emitting the monochromatic radiation of 540·10¹²Hz, radiant intensity of which in this direction is 1/683 W/sr. In this determination 683 lm/W – light metrological constant.

The ideology of construction of primary standard of candlepower unit, developed in the NSC “Institute of Metrology” is based on the application of absolute cryogen radiometer, with the help of which there is achieved a considerable progress in the accuracy of measurements of the power of optical radiation. On both the metrological and technical characteristics the measurement standard corresponds with the world level. With the help of absolute cryogen radiometer it is possible to build more optimal standard system in the field of spectrum radiometry. The determination specifies single-valued connection between light and radiant quantities.