Gretag Aktiengesellschaft

Robert Wahli

Armin Meyer

Bruno Brandli

Jorg Muller

Jurgen Pinkert

In a photofinishing operation, the correlation of order envelopes, films and the paper prints produced therefrom is carried out automatically. The order envelopes, films and the strip of paper prints are provided with the same machine-readable control number per order. These control numbers are monitored during final processing by machine and, in case of a lack of agreement, the cutting of the film and the paper is prevented and an appropriate alarm is actuated.

Process and apparatus for the preparation of photographic copies

A method for controlling exposure in the direct printing of color transparencies, the method comprising comparing the neutral density of an original transparency required to be printed with a reference transparency to obtain a measure of the difference in neutral density, this difference then being used to control the exposure time. Control is effected by increasing the exposure time for that portion of the density difference which exceeds a first positive limit by a predetermined amount which is less than the increase in exposure time required by the positive density difference below the first positive limit and decreasing the exposure time for that portion of the density difference which is less than a second negative limit by a predetermined amount which is less than the decrease in exposure time required by the negative density difference above the second negative limit. Apparatus for carrying out the method comprises a printing light source for illuminating the original and the reference transparencies and circuitry for obtaining the neutral density difference. Filters for interposing between the light source and the original transparency are controlled by a non-linear circuit which determines the amount by which the exposure is to be increased or decreased by the above predetermined amounts.

Process and apparatus for printing transparencies

An exposure control system for color printers having electro/optical means for spectral analysis of different types of original material for printing to determine different spectral coefficients for each material. Each coefficient is classified according to a reference range of values, each range being associated with a different original material. Photoelectric means are provided to determine the color densities of an original and a store stores sets of exposure parameters, each set being associated with a different original material. Automatic selection means responsive to the classification is provided to select whichever parameter set is associated with a coefficient reference range in which the coefficient has been classified during classification.

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Unterengstringen, Switzerland

Robert Wahli