GB1394975A - Photographic exposure control apparatus - Google Patents

Abstract

1394975 Cameras EASTMAN KODAK CO 9 Aug 1973 [9 Aug 1972] 37721/73 Heading, G2A A camera has an exposure control circuit which when the light intensity is average holds the shutter open for a photo-electrically determined period and when the light intensity is high closes the blades as soon as they open whereby the exposure period is mechanically determined. When the light intensity is low the exposure may be photoelectrically controlled or controlled by fixed resistor(s) switched in if flash is used. As shown, when a photo-cell 110 is illuminated by light of an average intensity a trigger circuit 104 is switched on and a low light indicator lamp 108 is not energized. On pressing the shutter release 60, a latch 50 releases an impeller 30 which strikes and opens a scissors-like shutter 12, 14. Movement of im- peller 30 also operates a switch 52 which connects contacts RS and CD. Contacts RS energize an electromagnet 106 which holds an armature 45 to arrest impeller 30 and thereby hold the shutter open. Contacts CD initiate charging of a capacitor 118 through photo-cell 110. When charged capacitor 118 switches off trigger circuit 104 to deenergize electromagnet 106 and release impeller 30 whereby spring 26 closes the shutter. If the light intensity is high trigger circuit 104 is non- conductive so electromagnet 106 cannot be energized and spring 26 closes the shutter as soon as it has opened. If the light intensity is low, lamp 108 is switched on and the operator has the choice of making a photo-electrically controlled exposure or a flash exposure. In the latter case, a switch 53 is closed to switch in a fixed exposure time resistor 114. An additional resistor 116 may be switched in when the camera is focused on near objects.