Abstract: A photographic color printer includes a color video camera for making specialty prints. A memory is provided to store different color compositions for printing light including an initial color composition and additional color compositions which surround the initial color composition. The memory also stores camera adjustment parameters for each additional color composition so that, when the color composition of the printing light is shifted away from the initial color composition, the camera can be adjusted to the new color composition. The camera is adjusted to the initial color composition by exposing the camera to light of this composition. Following such exposure, the camera is sequentially exposed to light of the various additional color compositions. The camera is adjusted to each additional color composition in order to obtain the camera adjustment parameters which are to be stored in the memory.

Abstract: A transparency to be printed is scanned to generate density values which are used to determine the degree of exposure of the transparency. The transparency is further scanned to generate signals representing an image of the transparency. The scanner which is employed for the latter scanning procedure and produces the signals has a linear scanning range and, based on the degree of exposure of the transparency, the illumination intensity or integration time of this scanner is controlled such that the master is scanned within the linear range. The signals generated by the scanner are corrected using a characteristic line selected in dependence upon the degree of exposure of the transparency, the color temperature and/or the film type. The corrected signals are processed to additionally enhance the image of the transparency and are then used to print the image.

Abstract: The gray balance of a color copying apparatus is adjusted by generating three sets of test signals respectively representing red, green and blue components of a test image. The test image is modified by operating on each set of signals with a respective characteristic line. The characteristic lines are stored in look-up-tables constituting part of the apparatus. Each characteristic line has a first point corresponding to a first location of the modified test image and a second point corresponding to a second location of the modified test image. A first copy of the test image is made and the red, green and blue densities of the copy at the first location determined. If any of these densities deviates from a reference value, the corresponding characteristic line is adjusted so that the respective density assumes the reference value. A second copy of the test image is now made and the red, green and blue densities of the copy at the second location determined.