GB807451A - Improvements in and relating to the shutter mechanism of photographic cameras - Google Patents

Abstract

807,451. Photo-electric control of camera shutters. GENERAL ELECTRIC CO. March 20, 1956 [March 31, 1955], No. 8673/56. Class 40 (3). A camera shutter has a power drive controlled by a photo-cell such that shutter operation is automatically initiated by a predetermined radiation change. In the embodiment described (see Fig. 4) shutter X is operated by armature 41 of relay 40 whose coil 42 is energized (i) via relay switch 46 controlled by conduction in thyratron 49 by A.C. from source S via the resistance between photo-cell conductors 31, 31<SP>1</SP> when reduced by incident light, or (ii) via relay switch 281 operated by bridge network R when incident light reduces sufficiently the resistance between the photo-cell conductors. In case (i) the shutter is adjusted for operation at a desired exposure interval setting, opening automatically in response to light on the photocell from for example an aerial flare and closing automatically at the conclusion of the desired interval by timing means not described; in case (ii) the shutter is opened prior to the incidence of illumination, e.g. at the instant of release of a photo-flash bomb from an aircraft, by the momentary closure of normally open switch 53 and the shutter is subsequently closed at a predetermined time after the incidence of illumination causes operation of relay switch 28, this predetermined time being a function of the resistance of resistor 54 connected via normally-closed switch 28<SP>1</SP> across relay coil 26. Switch 45 is as shown for case (i) and is changed over for case (ii). In an alternative to the bridge rectifier circuit, coil 26 may be in series with a rectifier and photo-cell conductors 31, 31<SP>1</SP>. Specifications 796,974 and 807,450 are referred to.