Colorimetry, Methods

Abstract

The perceived color of an object depends on the illuminating light source, the reflection or transmission of light by the object, and the response of the human observer. The numerical specification of colors, using the Commission internationale de l’éclairage (CIE) system of colorimetry, requires a spectral power distribution for the light source, reflectance or transmittance data in the visible region for the object, and defined numerical descriptions for the color responses of the observer. These data allow calculation of the three tristimulus values (X, Y, and Z), defining the color of the object, and these coordinates locate the position of the color in a 3-D color space. The difference in color between two objects is related to the distance between their respective points in the color space. The initially calculated tristimulus values are usually transformed into other coordinate systems, for example, the CIELAB system, to provide a more visually uniform color space in which the perceived difference in color of two objects corresponds closely to the separation of their points in the color space. Colorimetry has become a standard industrial technique for quality control and for colorant recipe formulation and modification.