TIME CONTROL ARRANGEMENT FOR PHOTOGRAPHIC CAMERAS

1,194,393. Photographic cameras. AGFAGEVAERT A.G. Sept. 19, 1967 [Sept. 30, 1966], No. 42535/67. Heading G2A. A circuit arrangement, in a photographic camera wherein the shutter is controlled by a photo-electric timing circuit comprising first and second part-circuits, each including a photoresistor, for different illumination ranges, includes change over means from one part circuit to the other and a photo-electrically controlled circuit indicating the range of illumination. As shown in the Fig., timing circuit 1 is a trigger circuit including transistors 3, 4, 5 the output energizing an electromagnet 7 which controls the shutter, and the input being controlled by an R.C. combination of photo-resistor 15 and capacitor 20, or photo-resistor 14 and capacitor 19. The indicating circuit 2 is a trigger circuit including transistors 24, 25 and lamps 27, 28 the input voltage being derived from a divider comprising photo-resistor 14 and fixed resistor 23. When main switch 31 is closed via the camera release (not shown) if the illumination is adequate for exposure, lamp 27 lights up and the shutter is opened by electromagnet 7 for a time depending on photo-resistor 15 and capacitor 20. If the illumination is less than the critical value, contacts 16, 18, 22 of the changeover are reversed, either mechanically or by a photo-electrically controlled switch, the shutter is opened for a time determined by photo-resistor 14 and capacitor 19, and lamp 28 lights up. In the bright ranges, the aperture may be set conjointly with the shutter speed.