Patent GB-451659-A (GB)
Title: Improvements in or relating to apparatus for controlling the transmission of light to sensitised photographic elements
IPC: G03B7/12
Filed: 1935-02-07
Abstract: 451,659. Controlling exposures in photographic and kinematographic cameras. KODAK, Ltd., Kingsway, London.-(Assignees of Mihalyi, J.; 333, State Street, Rochester, New York, U.S.A.) Feb. 7, 1935, Nos. 3932 and 3933. Convention dates, March 13, 1934 and Aug. 18, 1934. Addition to 451,658. [A Specification was laid open to inspection under Sect. 91 of the Acts, Aug. 9, 1935.] [Classes 97 (i), 98 (i), and 98 (ii)] In apparatus for controlling the transmission of light to sensitized photographic elements during exposure as described in the parent Specification, means are provided whereby the stop is looked in the position in which it has been set by the light sensitive cell prior to engagement of the stop by the mechanism which adjusts the exposure opening. As shown in Fig. 1, the film 61 is fed through the gate 60 by a claw 63. Transmission of light from the objective 62 to the film 61 is regulated by a diaphragm comprising two relatively movable plates 67, 68 having substantially rectangular openings 69, 70 and provided with slots 71, 72 engaged by a stud 73 on a lever 74 pivoted on a bolt 75. A photo - electric cell arranged in the camera front is electrically connected to a meter coil controlling a pointer 80 cooperating with a trap 83 comprising two toothed combs 84 provided with two arms 84<1> pivoted at 85, 86 on two supporting arms 87, 88. The arm 88 has a spur 90 forming a stop for a pin 91 on one arm 84<1>. The pivot 86 carries a spring 92 biassing the trap 83 out of engagement with the pointer 80. The diaphragm adjusting lever 74 has a stud 95 moving m the path of the pointer 80 and is biassed by a spring 97 to tend to maintain the diaphragm at its smallest effective aperture, but is held against the action of the spring 97 by engagement of a leg 99 with a pin 100 on an arm 101 integral with the lever 74. The leg 99 is integral with a member 102 vertically slidable on pins 103. The main operating lever 112 is secured to a shaft 111 carrying an arm 114 engaging the release trigger 65 for the camera mechanism. A link 110 is secured to a bell-crank lever 106 pivoted at 105 and connected to the member 102. On turning the lever 112, the leg 99 rises and permits spring 97 to rotate lever 74 until the stud 95 engages the pointer 80 held by the trap 83 rotated against the action of spring 92 by engagement of cam 115 on member 102 with an arm 84<1>. A detent pivoted on the bolt 75 engages a hook 119 on the member 102 to prevent operation of the mechanism until the lever 74 has been rotated. The detent can be moved from the path of the hook 119 by a rod 120 having a head 121 outside the camera casing. A second pointer on the meter shaft 81 co-operates with an externally visible scale. In a modification, the diaphragm comprises two blades vertically slidable on a pin, and provided at the bottom with oppositely disposed cam slots engaged by a pin on one arm of a bell-crank diaphragm adjusting lever, the other end of which engages a pin on the operating lever. The end of the operating lever co-operates with a cam on one of the arms carrying the trap. An auxiliary arm coaxial with and frictionally clutched to the diaphragm adjusting lever carries a pin engaged by an aperture on an index lever on depression of a knob adapted to be engaged in a series of notches, corresponding to different camera or emulsion speeds, in a slot in the camera front. Movement of the operating lever first traps the meter pointer and then moves the diaphragm adjusting lever and the auxiliary arm until the pin on the latter engages the meter pointer. Adjustment in accordance with the emulsion speed may also be effected by the provision in the film magazine of an indentation, the depth of which corresponds to the emulsion speed of the film, which is engaged by the end of a bellcrank lever which controls the effective length of one of the blades of the diaphragm. In a further modification, a grid limiting the angle of incidence of the light falling on the light sensitive cell is provided. with a grid shutter whose position is controlled by the depth of the indentation in the magazine. The position of the shutter may also be controlled by the camera speed-control lever. In a further modification the shutter is automatically controlled by the speed-control lever, but manually controlled in accordance with the emulsion speed. In a further modification, in which the camera is provided with two spring motors, the position of the grid shutter is controlled by an embossing on the magazine and also by the speed control member, which is provided with two cams, one controlling the governor disc and the other a lever controlling the position of the grid shutter. Specification 451,685 is also referred to.