| 摘要 |
<p>1293082 Photographic exposure control systems POLAROID CORP 5 March 1970 [5 March 1967] 10701/70 Heading G2A A photographic exposure control system has a shutter RC timing circuit having a photoresistor 80 and a capacitor 82, into which an additional electric signal is fed upon actuation of a flash illuminating device 158 to limit the exposure time to a predetermined value, the additional signal being derived from a power supply separate from that which actuates the RC timing circuit. The signal is present whenever a switch S 5 in the electronic flash converter circuit is closed, and is applied through a diode to prevent current drain from battery 86 when switch S 5 is open. For 'fill-in' flash exposures, capacitor 152 may be charged by closing switch S 5 , switch S 5 is then opened and the exposure made, the exposure time being determined solely by light incident upon photo-resistor 80.</p> |
