Reduced Photometric Quantities

quantities that characterize optical radiation in accordance with its effect on a specified selective optical detector. For any spectral composition of the radiation, to identical reactions of the selective detector there correspond equal values of the reduced photometric quantities. This is the principal advantage of such quantities, especially in the evaluation of radiation used for practical purposes. Each of the reduced photometric quantities is the integral of the product of the spectral sensitivity of the given detector and the spectral density of the corresponding energy quantity characterizing the radiation.

An international agreement has been concluded on just one system of reduced photometric quantities. In principle, it is possible to create systems of reduced photometric quantities to fit any detector. For example, there are used reduced photometric quantities that characterize the usefulness of radiation in the growing of plants. Other examples are bactericidal reduced photometric quantities, used to evaluate the germicidal action of ultraviolet radiation, and erythemal reduced photometric quantities, used to determine the useful effects of ultraviolet radiation on the human organism. The definition of new reduced photometric quantities is based on certain assumptions that require experimental verification. These assumptions concern the shape of the spectral sensitivity curves for the detectors and the degree to which the reactions of the detectors are subject to the laws of the additivity and interchangeability of the illumination and time factors.