Abstract: The color mixing compartment of illuminating equipment for a photographic enlarger includes two parts. The part adjacent the light-admitting surface is a truncated pyramid. The part adjacent the light-emerging surface is substantially a parallelepiped having side faces disposed substantially perpendicularly to the light-emerging surface. A diffusing plate having a substantially uniform thickness is arranged at the light-admitting and light-emerging surfaces of the mixing compartment.

Abstract: A mechanism, for adjusting the position of an illuminating lamp longitudinally and angularly in planes perpendicular to the optical axis of the condenser, has a lead screw and guide rod mounted substantially parallel to each other on the housing. The lamp socket holder is longitudinally traversed by the lead screw and the guide rod is eccentrically adjusted to impart a tilting movement to the holder. Control knobs for the lead screw and tilting mechanism are disposed adjacent each other on the outside of the housing. The lamp socket may also be axially and rotatably adjusted in the holder.

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: Three measuring channels in a photographic color printing and enlarging apparatus are utilized for determining the filter values of the primary colors. The exposure time is determined by adjusting and reading the amplification factor of an amplifier which amplifies the signal of a light-voltage transducer containing a photoelectric element, which obtains its input from a measurement of each of the three primary color components in the printing light. The light-sensitive element of the photoelectric element has a characteristic curve which is linearly related to the intensity of illumination and it is preferably a photodiode. The light impinging on the photodiode is modulated by an electromechanical light-chopping device and the measuring signal is controlled by a zero-regulator. The light-sensitive element, the zero-regulated device, the light-chopping device and filter controlling device are miniaturized and fitted into a light-measuring probe.

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.