Abstract: An illuminating system is provided with a source of light for generating a beam of light having a ratio of energy distribution at three wave length ranges that differ from the spectral sensitivity of photographic copying material at those three wave length ranges. Color filters are inserted into the beam of light to a depth for compensating for the disparity between the energy distribution and spectral sensitivity. One of the filters is of a filter color that influences the wave length ranges having the highest energy levels in excess of a desired energy; a second filter of a second filter color influences only the wave length range with the largest energy excess over the desired energy level.

Abstract: An apparatus for determining the color composition of the printing light of a photographic enlarger samples and measures the light within the intermediate diaphragm chamber of the objective lens. The light is sampled by inserting color-sensitized photoelectric transducers within the intermediate diaphragm chamber or inserting a light conducting means within the chamber between exposures for sampling and conducting the light outside of the chamber to external photoelectric transducer means, which determines the color content in any operative manner. The light conductor may be mounted on a slide together with an adjustable diaphragm for alternating inserting in the path of the printing light or the light conductor and a number of apertures of different cross-sections may be mounted on a rotary disk for optional insertion along the optical axis. The light conducting means includes a diffusing element within a light conducting and reflecting chamber.

Abstract: The color composition of printing light in a photographic enlarger is sampled by rotating a sampling duct between the original image holder and the objective lens. The duct has a thin elongated rectangular shape with a light diffusing aperture disposable in the printing light and with mirrored inside walls, which transmit a representative sample of the printing light to the outlet aperture, which is disposed in front of light measuring receivers. The receivers generate a signal which is processed to govern the insertion of filters in the light-mixing head of the enlarger to provide the desired color composition in the printing light. A convenient push control and actuating switch arrangement is provided to simplify insertion of the duct in the printing light before and its removal during the printing exposure.

Abstract: A blocking filter is used, in conjunction with the substractive filter method of copying photographic color images, to remove or substantially remove by greatly weakening wave lengths from the copying light in the range in which the filter characteristics of the blue and green color filters or the spectral sensitivity curves of photographic copying paper overlap each other, or more particularly in a 30 nm belt about a central wave length of approximately 500 nm.

Abstract: The filter insertion settings of a colored light projector are determined by projecting the colored light through different light color windows of a test probe onto a light measuring device to provide a predetermined signal. Diaphragms on the color windows are adjusted to provide a predetermined balanced format for a predetermined balanced light condition. The filters on the projector are adjusted for a given light, such as through a color negative to be printed, to cause the aforementioned predetermined signal to be generated by the light measuring device. Different settings on different probes may be provided for different series of predetermined desirable color formats or combinations, such as for different types of color negatives -- for example, for verdant scenes or sea scapes. The optical diaphragms may be conveniently provided by adjustable screws running into the windows.

Abstract: A color filter-determining apparatus, which indicates the color component to be balanced, has two measuring circuits, each of which contains a pair of photoelectric transducers. One of the photoelectric transducers in each measuring circuit is sensitive to the same primary color and the other transducers are sensitive to different primary colors. The measuring circuits comprise resistance measuring bridges, which are complemented by resistors and diagonally supplied by separate power sources and also diagonally connected to inputs of operational amplifiers, such as sum-and-difference amplifiers.

Abstract: This invention relates to a light-measuring apparatus wherein a photoelectric element is arranged in a leg of a measuring bridge, the output voltage of said element controlling the brightness of two signal lamps.