Visual Colorimetry Research Articles

The Colorimetry and Photometry of Daylight and Incandescent Illuminants by the Method of Rotatory Dispersion*

Further studies, both theoretical and experimental, have been made on the method of photometry and colorimetry previously proposed by the author.In the light of this work the method is now proposed as a complete and satisfactory solution of the practical problem of the visual photometry and colorimetry of all illuminants (including the important phases of daylight) whose spectral distribution approximates the Planckian formula closely enough to give a color match. This solution is based upon the principle of the additivity of homogeneous luminosities and the assumption of a standard visibility function.The method falls in the general class of substitution “equality of brightness” methods. All brightness matches are made at a color match. This color match is obtained by modifying the color of a constant comparison source by allowing its light to pass through a train of nicol prisms and quartz plates which form, in effect, a blue or yellow filter of continuously adjustable spectral transmission.Tables and graphs have been prepared by which color temperature and intensity may be readily obtained from the instrument readings on the basis of any visibility which it is desired to assume as standard.