Patent GB-468315-A (GB)
Title: Improvements in photographic or cinematographic cameras with photoelectric exposure meters
IPC: G03B7/04
Filed: 1936-08-12
Abstract: 468,315. Photographic and kinematographic cameras. TATE, F. R. (Zeiss Ikon Akt.-Ges.) Aug. 12, 1936,. No. 22242. [Classes 97 (i) and 98 (i)] The resistance in circuit with the photo-electric exposure meter of a camera is adjustable in accordance with the various exposure conditions such as exposure time, diaphragm opening, film sensitivity and colour filters by connecting the movable contact and resistance to at least one of the adjusting means, any two or more of the adjusting means which are connected either to the resistance or contact being connected to one another by releasable couplings. In the camera shown in Fig. 2, the diaphragm adjustment ring 13 is carried on a ring 4 connected by a releasable coupling 14 to a second ring 18 connected by a releasable coupling 15 to a ring 20 carrying a gear wheel 5 engaging a rotatable resistance 11 through gears 6, 7, 8. The movable contact is connected to the knob 2 for adjusting the exposure time, and to prevent movement of this knob and of the contact on winding or releasing the shutter, the gear train shown in Fig. 4, is employed. The knob 3 winds the film on to the spool 23 through a gear train 75, 76, 77, 78, the gear 78 being mounted on the spool shaft 72, freely rotatable within the knob 3. To wind the shutter the gear 76 drives a gear 79 which is free on the shaft 73 of the knob 2, the gear 79 having internal teeth engaging a planet gear 81 on a disc 82, the gear 81 also engaging an inner gear 80 fixed to the shaft 73. The disc 82 is connected by coupling pins 83, 84 to a gear wheel 85 which is axially movable against spring action and which winds the shutter 24 through gears 66, 87, 88. Since the gear 80 remains stationary the contact is not moved by the shutter-winding operation. To release the shutter a knob 89 is depressed to move the disc 85 axially, the pins 83 and 84 thus becoming disengaged and the shutter released for exposure without affecting the winding knob 3. The resistance 11 is connected in parallel with the photo-electric cell 1 and the indicating instrument 10, Fig. 5. The operation is as follows : If, for example, the exposure time is to be found when the aperture has been decided, the ring 4 is rotated to adjust the diaphragm according to a scale on the ring 4, this rotation also moving the resistance relative to the contact. Adjustment is then made for film sensitivity by releasing the coupling 14 and rotating the rings 18, 20 and the resistance relative to the ring 4 until the appropriate figure of the Scheiner scale 16 appears in an aperture in the ring 18. For adjusting for the filters used in accordance with a scale 17, the coupling 15 is released and the ring 20 rotated relative to the rings 4 and 18. The deflection of the instrument 10 is then returned to a fixed value by adjusting the contact, which automatically sets the exposure time. The procedure is similar if the diaphragm aperture is to be determined. In an alternative arrangement the resistance is directly connected to the diaphragm adjustment member, and the contact is connected through a releasable coupling to the exposure-time adjustment member and to a member carrying a Scheiner scale. In a kinematograph camera, Fig. 7, the diaphragm-adjusting ring 47 and the rings 41, 42 are connected together and to a gear 53 in the same manner as that shown in Fig. 2, and the gear 53 is connected through gears 54, 55, 56 to a worm 57 engaging a gear 58 carrying the movable contact 44 of the resistance 43. The resistance is carried on a rotatable disc bearing planetary gears 67, 68, Fig. 9, engaging concentric gears 66 and 70 respectively, the gear 66 engaging also a gear 90 carrying a cam surface 92 which actuates a lever 93 bearing on a centrifugal governor 61 connected to the driving mechanism so that rotation of a knob 59 rotates the gear 66 to move the resistance and to adjust the speed of the mechanism. The gear 70 engages a gear 69 connected to an adjustment knob 64 and having a cam 100 engaging a pivoted lever 94 which engages a sliding sleeve 96 on the rectangular shaft 97 of the shutter, the sleeve having a pin 99 engaging a slot 101 in the hub of the blade 63 of the shutter 62, 63, so that rotation of the knob 64 to adjust the resistance causes the blade 63 to rotate relative to the blade 62 to vary the aperture of the shutter and hence the exposure time. The arrangement of gearing is such that adjustment of either of the knob 59, 64 does not affect the other.