A Proposed Method for Computing Colorimetric Densities

The Colorimeter holds tremendous promise for color measurement in the Printing Industry. Yet, the measurements provided by the colorimeter are different from those provided by more traditional instrument, the densitometer, making interpretation of colorimetric measurements (in the context of the industry) difficult. This is a significant obstacle to the acceptance of the colorimeter as a pressroom tool. Simple conversion of the X, Y, Z, tristimulus values into densities is not satisfactory for most purposes. The Preucil coordinates of Hue, and Greyness, which are used in color correction , are distorted when using colorimetric densities based on X, Y, and Z. This is because these tristimulus values correspond not to actual Red, Green, and Blue stimuli, but to over-saturated stimuli with slightly different hues. This paper discusses the transformation of the XYZ tristimulus values to a RGB-space. Because a linear transformation from XYZ to RGB is used, the new coordinates will be colorimetrically based . The new coordinates may be used directly in the computations of such parameters as Preucil Hue and Greyness. Transformation to uniform color spaces, such as CIELAB and CIELUV, is both exact and simple to perform. Simple conversion of the X, Y, Z, tristimulus values into densities is not satisfactory for most purposes. The Preucil coordinates of Hue, and Greyness, which are used in color correction , are distorted when using colorimetric densities based on X, Y, and Z. This is because these tristimulus values correspond not to actual Red, Green, and Blue stimuli, but to over-saturated stimuli with slightly different hues. This paper discusses the transformation of the XYZ tristimulus values to a RGB-space. Because a linear transformation from XYZ to RGB is used, the new coordinates will be colorimetrically based . The new coordinates may be used directly in the computations of such parameters as Preucil Hue and Greyness. Transformation to uniform color spaces, such as CIELAB and CIELUV, is both exact and simple to perform.