Patent GB-1443188-A (GB)
Title: Photographic camera and electronic flash device combination
IPC: G03B9/70
Filed: 1973-10-22
Abstract: 1443188 Cameras WEST ELECTRIC CO Ltd 22 Oct 1973 [23 Oct 1972 20 March 1973] 49030/73 Heading G2A A camera has a light detecting circuit for selecting daylight or flash photography, a switch coupled to the focusing ring which allows the flash tube storage capacitor to be charged only if the object is within the range of the tube, and a shutter blocking mechanism which, if flash photography is selected, blocks shutter release until the storage capacitor is charged. In Fig. 1 if the object is within range a switch 23 coupled to the focusing ring 24 is opened and if the light detecting circuit 1 selects flash photography it turns on a thyristor 10 which via transistors 6, 29 and 27 turns off a transister 7 to initiate charging of a storage capacitor 4 and via transistors band 11 turns an electromagnet 20 off to block shutter release. When capacitor 4 is charged it turns on a tube 8 which turns transistor 6 off to energize electromagnet 20 and allow shutter release. If the object is too distant for the flash tube, switch 23 is closed. This turns on a transistor 39 which energizes a light emitting diode 22 to warn the photographer and to turn on transistor 7 which prevents capacitor 4 being charged. If daylight photography is selected by circuit 1, thyristor 10 is not turned on so capacitor 4 is not charged and the shutter is not blocked. In Fig. 3, pressing the shutter release firstly closes a switch S which energizes an electromagnet 67 if the battery is working and this closes a switch 68 to light an indicator lamp 69. A switch 63 connected to a photo-conductor 74 is then closed whereby if the light is strong enough for a daylight exposure a thyristor 71 is turned on which via transistors 59, 64 and 66 turns off the electromagnet 67 which opens switch 68 and extinguishes lamp 69. If flash is necessary thyristor 71 stays off and so switch 68 stays closed. Thus when a switch 77 is subsequently closed a thyristor 79 is turned on which via transistors 82, 87, 83 turns off a transistor 86 to initiate charging of a flash storage capacitor and via transistors 82 and 66 turns off the electromagnet 67 to block shutter release. When the capacitor is charged it turns on a tube 90 which via transistors 91, 66 energizes electromagnet 67 to allow shutter release. Tube 90 also turns on transistor 92 so that when a switch 78 is closed transistors 93 and 73 are turned on and 94 off whereby the photo-conductor 74 is replaced in circuit by a variable resistor 95 coupled to the focusing ring. The shutter is opened and on opening switch 76, a capacitor 80 charges through resistor 95 to turn thyristor 71 on and turns transister 64 off. This turns a transistor 96 on to send a firing signal to the flash device 106 and also de-energizes the electromagnet 67 to close the shutter. For daylight exposure the capacitor 80 charges through the photo-conductor 74. If the object is too distant for flash exposure, a switch 81 is closed to turn on a warning photodiode 102 and the transistor 86 which prevents the storage capacitor being charged. A manual over-ride switch 105 is provided and is coupled to a filter movable in front of lamp 69 to indicate operation of switch 105.