GB1249384A - Photographic exposure control mechanism - Google Patents

Abstract

1,249,384. Shutter control arrangements. HATTORI TOKEITEN K. K. Feb. 24, 1969 [Feb. 28, 1968], No. 9711/69. Heading G2A. The exposure terminating member 39 of the shutter described in Specification 1, 249, 386 makes a preliminary movement towards its exposure terminating position for daylight exposure operation, but is held in its initial position for flash exposures. The control circuit, Fig. 2, enables the electromagnet 50 to be energized to thus hold member 39 by actuation of switch 5 1 if the photo-resistor 56 indicates insufficient light for daylight exposure and if the flash circuit consisting of bulb 56, switches 51 and 55 and pilot lamp 57 indicate that the flash circuit is in an operative condition. If sufficient illumination is present or if the flash circuit is faulty then the closure of 51 does not effect the energization of the electromagnet 50, the continued movement of release lever 1, Fig. 1, causes the nose 5 thereof to engage lever 36 to commence the movement of member 39, the subsequent closure of switch S 2 renders transistor T 2 conductive to energize electromagnet 50 and stop the movement of member 39. In daylight operation, the opening of the shutter opens contacts S 40 to start operation of an RC timing circuit formed by capacitor 57 and the photo-resistor 56, after the measured time, transistor T 2 is rendered non-conducting to de-energize electromagnet 50 and thus close the shutter. In flash operation, the opening of the shutter closes contacts S 41 which completes the flash circuit, the sudden drop in voltage on firing of the bulb being sufficient to de-energize the electromagnet 50 and close the shutter. Switch S 5 is closed only if member 39 does not make an initial movement.