Patent GB-792730-A (GB)
Title: Improvements in and relating to photographic cameras
IPC: G03B7/04
Filed: 1955-09-23
Abstract: 792,730. Photographic cameras. DECKEL, H., and DECKEL, F. W. Sept. 23,1955 [Oct. 1, 1954], No. 27195/55. Class 98(1) [Also in Group XL(b)] In a photographic camera with a between-lens shutter and photo-electric exposure meter the pointer of which is adjustable when setting the shutter speed by varying at least one resistance in the meter circuit to a position dependant on the shutter speed or diaphragm setting, the means for varying the resistance also constitute a disconnectable coupling between the shutter-speed-setting and stop-setting elements. As shown in Fig. 3, an interchangeable lens and shutter assembly 18 is fastened by a bayonet joint to a tapered lens tube 12 fixed to the front of the camera. The shutter assembly carries rotatable on the periphery thereof a setting sleeve 42 with knurled grip 44 connected to the shutter speed setting element 34, and a setting sleeve 46 with knurled grip 48 connected to the diaphragm setting element. 38. Each setting ring carries a scale, which is read against a fixed mark on a fixed ring 56 fastened to the-shutter housing. A spring lug 58 is connected to the shutter-speed setting element 34 and extends through a recess in the ring 56 to engage one of a number of coupling teeth 62 in the inner side of the setting rings 46. The lug 58 thus provides a disengageable connection between the setting ring 42 and 46. As shown in Fig: 4, a photo-electric cell 66 receiving light through a window 64 in the front of the camera is connected to a'meter 68. The pointer 72 is visible in a window 74 in the top of the camera, and may be brought into register with a fixed mark 76. Marks 78, 80 are provided to indicate in which direction adjustment should be made to bring the pointer back to the mark 76. The deflection of the meter pointer is controlled by a variable resistance 82 connected between the meter and the cell 66. The body of the resistance 82 is mounted by means of insulating material on the diaphragm setting member 38, while the moving contact 84 is connected to the spring lug 58 carried by the shutter speed setting member 34. As shown in Fig. 3, the connection from the meter to the resistor 82 is made through a pin 88 extending through an opening 90 in the shutter housing to a contact strip connected to the resistor. In use, the camera is directed towards the scene to be photographed, and the setting ring 42 is rotated with respect to. the setting ring 46 until the meter pointer 72 is brought opposite the mark 76. The rings 42, 46 are then held together by spring lug 58 and may be rotated together to select the most convenient combination of shutter speed and diaphragm aperture. Fig. 6 shows the manner in which three resistances 82a, 82b and 82c may be connected in the photo-electric cell circuit, so that the resistance in series with the photo-electric cell is always constant. Factors effecting the required exposure, such as the sensitivity of the film emulsion, may be allowed for by including regulating resistances in the circuit, by displacing the moving contact of the resistance with respect to the shutter speed setting member 34, or by rotating the body of the meter. A second photo-electric cell may be connected in parallel with the first to increase the sensitivity of the instrument for use in weak light.