Patent GB-392902-A (GB)
Title: Means for setting the diaphragm or shutter of a photographic camera
IPC: G03B7/085
Filed: 1931-10-23
Abstract: 392,902. Cameras. RISZDORFER, 0., 13, Avar-utca, Budapest. Oct. 23, 1931, No. 29509. Convention date, Oct. 23, 1930. [Class 98 (i).] For automatically setting the diaphragm (or alternatively the shutter) of a camera in accordance with the intensity of the light, a photoelectric cell 11, Fig. 1, is used in circuit with a battery 13, meter 10, a set of variable resistances 16, 17, 18 and a magnet 19, the armature 21 of which rotates against the action of a spring 23 and is operatively connected (as by link 28) with the diaphragm 15 (or the shutter). The resistances 18, 17 are pre-set in accordance with the shutter speed (or diaphragm, as the case may be), and the emulsion sensitivity. The resistance 16 may be a pre-set trimming resistance, or may be graduated for other factors affecting the exposure, (e.g. the filter used.) In action, as illustrated, the diaphragm 15 is normally fully open. For a high shutter speed the pre-set resistance 18 is proportionately large : the circuit current will be proportionately low when the cell is exposed, and the diaphragm 15 will be closed to a proportionately small extent. Similarly the resistance 17 will be pre-set to a comparatively high value for a slow speed emulsion, thereby resulting in a comparatively large diaphragm. The Specification as open to inspection under Sect. 91 also includes the matters of Specifications 394,716 and 395,763, and in addition two alternative means for setting a lens diaphragm preliminarily to an exposure. One arrangement, Fig. 5 (Cancelled) comprises (1) a relay 13 in the photo-electric cell circuit 11 which rotates an arm 14 to a position dependent on the light action on the cell Z ; (2) a clockwork motor 40 which is geared to open gradually the lens diaphragm 27 and has a rotating arm 15, 15<1> ; (3) an independent circuit 16 which includes a magnet 41 and is completed when the arm 15<1> contacts with the arm 14, the armature 42 being then operated to arrest the clock-work motor 40 and hold the diaphragm 27 in its correct setting for an exposure. The greater the light intensity the greater will be the swing of the arm 14 from its initial setting towards the arm 15<1>, and in consequence the smaller the extent to which the'lens diaphragm 27 is opened. The other arrangement comprises a diaphragm Z, Fig. 6 (Cancelled), through which the photo-electric cell is exposed and which is geared with the lens diaphragm A of the camera. The cell circuit 11 includes a relay 54 having a movable pointer 14 which moves towards a contact 55 in a circuit 17. This circuit 17 includes a motor 50 for synchronously closing the diaphragms A, Z from fully open initial position. After the cell is exposed for a certain time the pointer reaches the contact 55, and the motor 50 then progressively closes the diaphragms A, Z until the current in the cell circuit 11 is reduced to a value at which the pointer 14 leaves the contact 55 and stops the motor 50. The more intense the light the smaller the resulting setting of the diaphragm A and vice versa. The above matters do not appear in the Specification as accepted.