Abstract: The subject of the invention is a method and a device for generating a digital lookup table for printing inks in image reproduction equipment. Color scan values obtained by photoelectric scanning of an original are used for this purpose. The full colors of the three printing inks and white are measured. Model colors are determined which are in as linear as possible a relationship to the printing inks. This is achieved by a position of the chromaticity range of the print scale such that the primary stimuli of the model colors in the chromaticity diagram are each on one beam of the trajectories of the scale colors through the white point while the triangle set up between the primary stimuli encloses the chromaticity range of the print scale. The scale division of the primary stimuli is adjusted with a cube root to the printing inks. The number of fields to be scanned is determined on the basis of the measured values of the space diagonals. A cubic spline interpolation follows to generate the lookup table.

Abstract: A method and apparatus for color stimulus specification-correction, i.e. sensation-correction pickup for scanning of chromatic image originals, referred to in short as a multispectral scanner. A color image pickup system is provided, based on the multispectral principle, the plurality of I>>3 narrow-band spectral filters and one black filter being introduced into the optical beam path of the image scanner, and thus I narrow-band spectral separations of a color image original and of a white image original are registered and digitized. Spectral pixel samples individually calibrated for all pixels are formed with an electronic evaluation unit in pickup real time. These are either stored in I parallel image storage levels or are multiplied by specific coefficients from a table in pickup real time of the signals in three parallel channels and are accumulated in three parallel image storage levels.

Abstract: The color scanning signals generated by scanning the original are first converted into three primary color signals having actual color values in a predetermined color coordinate system corresponding substantially identically to theoretical color values of the original. It is only after this conversion that the primary signals or signals derived from these signals are converted to another color rendition system, or the gradation is altered, or the color rendition of individual colors in the overall image or in discrete areas is altered, or any other non-linear processing takes place.