Application of Principal Component Analysis in the Evaluation of Optical Detail Transfer Behavior in Offset Printing

Optical detail transfer characteristics of a chosen paper type were determined on a printed line grid with graduated column width with the help of a computer-linked microdensitometer. Signal amplitude, signal-noise ratio and the contrast transfer function were calculated based on the established optical density distributions perpendicular to the line grid taken from 78 prints. As a result of locally occurring discrepancies on the printed paper areas as well as statistical measurement errors, reliable approximation of the measurement data based on spatial frequency was not possible through analytical functions. Spectral break-down of the interference-ridden data through the application of principal component analysis enables the establishment of the relevant portion of information from the optical parameters. Through the extraction of the principal components, strikingly different contrast transfer behavior, based on spatial frequency, was found related to the direction of the paper fiber.