Patent GB-931562-A (GB)
Title: Photographic camera with an exposure regulating device
IPC: G03B7/12
Filed: 1959-11-03
Abstract: 931,562. Photographic cameras. AGFA A.G. Nov. 3, 1959 [Nov. 5, 1958], No. 37329/59. Class 98 (1). In a photographic camera having an exposureregulating device including shutter speed and diaphragm setting rings and a common setting member coupled to said setting rings by a differential mechanism, the regulating device is spring-loaded into an idle position in which each of the setting rings rests at one end of its range of setting movement and the common setting member is arranged to transmit variable setting movement to the setting rings via the differential mechanism and a manually-operable means is provided for selectively arresting one or other of the setting rings against movement by the setting member. In the camera shown a diaphragm aperture-setting ring 5 and an exposure time-setting ring 6 are rotatably mounted on tubes 7, 10 and are coupled together by a pinion 13. The movements of rings 5, 6 are limited by stops 41, 44, which engage recesses in the tubes 7, 10 respectively, and also by stops 55, 56 arranged in coaxial rotatable preselectors 57, 58 and respectively movable in recesses in the setting rings. The two preselectors 57, 58 are coupled together by a pinion 61 on the axle of a bevel wheel 64 which meshes with a bevel wheel 65 on a hollow spindle 66. The spindle can be turned by a knob 67 to set a mark 74 on it opposite a scale carrying two indicating marks on the camera housing, which marks correspond to respectively maximum depth of focus, i.e. smallest aperture, when the shutter is set at its slowest speed and greatest sharpness of a moving subject, i.e. highest shutter speed, when the diaphragm is at maximum opening. A setting control device comprises a rod 16 connected by a pin-and-slot connection 14, 15 to an arm 8 on which pinion 13 is rotatably mounted. At the end of rod 16 are two stepped cams 21, which co-operate with pointers 24 of an exposure meter galvanometer 23 connected to a photo-cell 93. If, as shown, the knob 67 is set for the greatest sharpness of a moving subject the preselectors 57, 58 are set so that stop 55 engages edge 52 of the diaphragm setting ring. Thus on depressing the rod 16 until one part of steps 21 engages the pointer 24 the pinion 13 runs along the stop ring 5 while the ring 6 is rotated and the exposure time is decreased. If, however, the light intensity is so high that before the stepped end of the rod engages the pointer 24 further increase of shutter speed becomes impossible, continued movement of the rod 16 will move the ring 5 to decrease the aperture since the force applied to the rod is sufficient to over-ride a presetting control brake comprising spring 91, ring 92 and disc 90, on the shaft 66. Similar considerations apply when the maximum possible depth of focus is desired, but here the diaphragm is first closed and then the shutter speed is increased. Rings 5, 6 have pointers 49, 50 which are located in the view-finder field 3 (or which are illuminated by a separate window and are imaged by a mirror in the field) and which by their positions indicate the depth of focus and degree of sharpness of moving objects respectively. If the operator is dissatisfied with the readings thus indicated, by rotating the knob 74 while knob 17 is held depressed he may adjust simultaneously rings 5, 6 until the required readings are obtained. Pressure on the knob 17 after rod 16 has been arrested, compresses spring 1.8 and a projection 25 on knob 17 engages a two-armed lever 28 and rotates it about a pivot 27 thereby, through rod 29 moving a cam 32 out of the path of a shutter-release arm 70 as long as the knob 17 is held depressed. This arm is connected to a knob 69 by a shaft 68 and when knob 69 is depressed, arm 70 co-operates with the shutter-release lever 73. In another embodiment the pinion 13 and racks 11, 12 are replaced by a pivoted lever having two forked ends embracing pins on tne rings 5, 6 and a lever having two arms is pivoted on the camera housing so that when knob 17 has finished its downward movement a notch on the knob engages a pawl on one arm of the lever which is spring-urged to hold the knob and rod 16 depressed. However, when the shutter is released, arm 70 engages a cam on the other arm of the lever and rotates it; thereby moving the pawl away from the notch and releasing the knob 17 and rod 16. The toothed gearing of the preselectors may be replaced by friction gearing.