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.