GB664790A - Variable apertured viewfinder - Google Patents

Abstract

664,790. View-finders. GAINSBOROUGH PICTURES (1928), Ltd., and HILL, G. E. May 11, 1950 [May 17, 1949], No. 13155/49. Classes 97 (i) and 98 (i). A view-finder comprises a viewing lens, a housing enclosing two relatively movable and overlapping mask elements which define a rectangular aperture, each mask element having projecting pins, a plate fixed to the housing and having guide slots engaged by the pins of the mask elements to control the relative movements of said elements, and a plate rotatable relatively to the housing, and having two cam slots, each of which is engaged by one of the pins carried by each mask element, each of said plates and said housing having an aperture coaxial with said rectanguJar aperture. The device shown comprises a fixed plate 2 forming the housing and having an annular flange 6, the outer surface of which is graduated in terms of focal lengths, and two annular shoulders 7 and 8. Seated by shoulder 8 and secured to plate 2 by screws 9 is another plate 3, which has therein slots 12, 12a, 13 and 13a through which pass pins 14, 14a, 15 and 15a, respectively, which project from masks 1 that are sandwiched between the plates 2 and 3 and define a rect. angular aperture registering with the central apertures 5 in the fixed plates. The slots in plate 3 extend parallel to a diagonal of the aperture defined by the masks and the pins 15, 15a on the latter also pass through cam slots 17 and 17a in a disc 16 which is rotatably mounted on plate 2 and secured by it pin 21 and slot 20 to a plate 18 carrying a viewing lens 19. Plate 19 is provided with a pointer 23 and, in use, is rotated until this pointer registers with the graduation on flange 6 designating a particular focal length. The size of the rectangular aperture then indicates the field of a camera lens of that focal length. In a modification, the plate 18 is rigidly mounted on plate 2 and a pointer is provided on the disc 16 for cooperation with the scale on flange 6, this pointer being visible through a cut-away part of plate 18. The disc 16 is in this arrangement rotatable relatively to the plates 6 and 18.