GB426404A - Devices for automatically operating the diaphragms of photographic and cinematographic cameras according to the intensity of light - Google Patents

Abstract

426,404. Exposure meters. PRINSEN, F. B. A., 16, Namenschestraat, Scheveningen, Holland. Oct. 3, 1933, Nos. 27195 and 27196. Convention dates, Oct. 4, 1932 and July 7, 1933. [Class 98 (i)] [See also Group XL] A device for automatically controlling the lens aperture of a photographic camera comprises a photo-electric cell directly connected to the moving-coil 11 of an electrical instrument, the diaphragm 12 being rigidly connected to the moving coil and provided with a tapering slit so that the light passed to the lens is inversely proportional to that falling on the cell. The photo-electric cell 13 comprises a flat copper tray within which is located a copper-cuprous oxide plate, is closed by a glass plate, and filled with a fatty acid. The poles of the field magnet 10 are shaped to modify the aperture, and the moving-coil instrument has an internal resistance matched with that of the cell 13. Screens 14 shield the cell 13 from direct illumination, and filters or shutters may be provided to vary the light intensity energizing the cell. A modified construction has two diametrically opposite diaphragms each operated by a coil movement. The Specification as open to inspection under Sect. 91 comprises also the following. The diaphragm is adjustable by resistances adapted to be switched into the electrical circuit. Instead of a diaphragm provided with a tapered slit, a grid diaphragm can be employed. The durations of exposure are plotted on a part movable with the instrument coil, Fig. 7 (Cancelled). The stationary scale member, or a part of it, Fig. 9 (Cancelled), may be displaced or rotated to obtain an adjustment for sensitivity of material and the filter used. This subject-matter does not appear in the Specification as accepted.