Patent GB-950201-A (GB)
Title: Improvements relating to photographic cameras
IPC: G03B17/02
Filed: 1960-08-26
Abstract: 950,201. Photographic cameras; lens mounts; diaphragms. LA SPIROTECHNIQUE. Aug. 26, 1960 [Sept. 4,1959], No. 29570/60. Headings G2A and G2J. A photographic camera having a depth-offield indicating system comprises two contrarotating depth-of-field indicator members respectively carrying indexes movable in visual registry with a focus-range scale carried on a rotatable ring of the focusing mechanism, a stationary focus index in registry with said focus scale, a diaphragm actuating ring rotatable coaxially with said ring of the focusing mechanism and coupled to studs respectively engaging arcuate slots in the diaphragm blades for setting the position of each blade about its respective stationary pivot, a diaphragm aperture scale formed on one of said two contra-rotating depth-of-field indicator members and rotatable in union with said diaphragm actuating ring, an aperture index member carried on the other said indicator member in visual registry with said aperture scale for showing the aperture setting, and a linkage between said diaphragm actuating ring and said depth-of-field indicator members for positioning said members in accordance with the diaphragm setting, the arrangement being such that depth-of-field indications are given in compliance with the law of variation of the depth-of-field as a function of focus and diaphragm settings, said system being characterised in that the markings on the diaphragm aperture scale have spacings therebetween which increase logarithmically as the aperture decreases,the arcuate driving slot of each diaphragm blade is traced in compliance with the said spacing of the aperture scale markings and the linkage between the diaphragm setting ring and said depth-of-field indicator members is linear. As shown (Fig. 3) diaphragm blades 32 pivoted about stationary pins 34 are coupled to a diaphragm adjusting knob 118 by way of pins 28 engaging in arcuate driving slots in said blades, a control ring 26 carrying said pins 28 and rotatably mounted on a non-rotatable lens mount 4 and a rotatably mounted ring 38 having a pin and slot coupling 42, 40 with the ring 26 so as to allow for relative longitudinal movement between the said rings and having teeth engaged by a bevel pinion 18 connected to the knob 118. Said bevel pinion 18 also engages with a ring 20 (Figs. 2 and 3) bearing an index 25, a further index 24 being carried by a segment 16 coupled to the ring 38, the arrangement being such that on adjustement of knob 118 the indexes 24, 25 rotate in opposite directions and indicate the limits of the depth of field on a distance scale carried by a rotatable ring 12 (referred to later). Segment 16 carries a diaphragm aperture scale and ring 20 an index mark 22 for co-operatio. therewith. Focusing mechanism comprising an objective lens mount 4 is mounted in a sleeve 62 by means of a screwthread 5 but is prevented from rotating by means of a longitudinal pin and slot connection 128, 41. Sleeve 62 engages by means of a further screwthread 64 with an objective casing 67 and is coupled to a focusing knob 110 by way of a rotatable but axially fixed tube 60 having a pin and slot connection at 66 with said sleeve 62 and having teeth engaged by a bevel pinion 10 connected to said focusing knob 110. Ring 12 carrying the focusing scale is connected to the tube 60 and an index 14 for cooperation with said scale is carried by a fixed ring 46. The objective casing 67 is connected to the camera face 74 by means of a bayonet coupling 70, 72. The camera is sealed in a fluidtight manner by means of a window 36 held in position by a ring 68 and by an outer camera casing 78, plastic packings 44, 80 and 82 also being provided for this purpose.