Programmable fully automatic shutter system for photographic cameras

Abstract

Upon exposure initiation, a shutter opens abruptly, an exposure-light diaphragm begins to open progressively, and a control diaphragm, behind whose aperture the light sensor is located, also begins to open progressively. The signal from the light sensor is integrated, and when the requisite total-light amount is reached the shutter falls closed abruptly. Accordingly, the system decides, on its own, what the exposure duration and exposure-light aperture size upon exposure termination will be. The user, however, can modify this fully automatic selection in the sense of longer exposures and smaller aperture, or else shorter exposures and larger aperture, by varying the motion-retarding force supplied by an electromagnetic motion retarder, which controls the speed at which the exposure-light aperture opens up. Prior to exposure initiation, the control aperture is at a minimum, but non-zero size, permitting scene-light-sufficiency measurement. The motion-retarding force is automatically lowered in response to temperature decreases and automatically boosted in response to scene-light increases, to counteract low-temperature slowness of mechanical movements and to prevent the need for unrealizably brief exposure durations. The electromagnetic motion-retarder is not connected to a current source, but instead generates magnetic motion-retarding force in response to movement of inductance-modifying structure in accordance with Lenz' law. When the user wishes to predispose the fully automatic system towards longer or shorter exposure durations or larger or smaller aperture sizes, the light-sufficiency indicator is automatically adjusted to take this into account.