Patent GB-900297-A (GB)
Title: Improvements in and relating to photographic cameras
IPC: G03B7/00
Filed: 1958-07-04
Abstract: 900,297. Photographic cameras with coupled exposure meters. VOIGTLANDER A.G. July 4, 1958 [July 10, 1957], No. 21516/58. Class 98(1). In a camera having an iris diaphragm the leaves of which are engaged at one end in a leaf pivot ring coupled with a time setting member for the shutter and at the other end in a leaf-actuating ring coupled with an independently manually adjustable diaphragm setting member, the leaf-actuating ring is coupled with mechanism within the objective mounting and the camera body by means of which a follower can be adjusted along the path of the pointer of a photo-electric exposure meter built into the camera. As shown, each of the diaphragm leaves 3 is carried by two independently rotatable rings 7, 9, relative movement of rings altering the aperture. The ring 7 is connected by a pin 11 to the shutter time setting ring 12 which is connected as at 18 to the shutteroperating mechanism 19 controlling blades 190 and which is provided with a knurled manuallyengageable rim 13 contacted by a retaining friction ball 17 and bearing setting marks 14, 15, or a single mark, co-operating with a shutter speed scale 16 and a diaphragm aperture scale 20 on the diaphragm setting ring 21. This ring is connected at 23 to the diaphragm operating ring 24 which has a slot 26 receiving a lug 27 on the ring 9, a friction ball 25 retaining the ring 24 against unintentional movement. An exposure value ring 28 is coupled to the ring 21 by a manually depressible spring catch 37 on the ring 21 engaging one of a series of teeth 35 on the ring 28, and also at 31 to a cam ring 32 having a follower 34 connected to a follow-up mechanism for the needle of a photo-electric light meter as in Specification 863,871. In use the catch 37 is first released to allow relative rotation of the rings 21, 28 to take account of the speed of the film used, a scale 38 of film sensitivities on the cam 32 being visible through an opening 380 in the ring 21. Thereafter, on re-engagement of the latch 37 simultaneous rotation of the rings 21, 28 to bring the followup member into line with the needle of the light meter sets the aperture to the value appropriate to the shutter speed set by the ring 12 for the exposure value selected. Thereafter ring 13 may be adjusted to select different combinations of aperture and speed giving the same exposure value. If in attempting to set a chosen shutter speed the maximum or minimum aperture is reached before the desired speed setting is attained, continued movement of the ring 12 is effected against a manually sensed resistance due to a pin 40 on the ring engaging the end of a slot 39 in the ring 21 and carrying the ring 12 with it so that the operator is warned of an incorrect aperture and speed combined setting. To make allowance for light weakening elements, e.g. filters in the path of the exposing rays, after setting the follow-up member in line with the light meter pointer, the ring 28 may be rotated so that a desired " filter factor " on the scale 29 is brought opposite a fixed mark 30, this adjustment for " filter factor " being necessary after each adjustment of the follow-up member.