Abstract: A pentagonal prism holder for holding a pentagonal prism in horizontal and vertical directions is made of a transparent plastic material and at least a portion of the prism holder is formed as an element or elements of an auxiliary or supplemental optical system or a finder optical system. The auxiliary or supplemental optical system may be one that indicates photographic information in the finder view field, an optical system for photometry, an optical system for preventing a ghost from being observed in a viewfinder, or an optical system for preventing undesirable or stray light passing through an ocular lens from entering into the pentagonal prism. The element of the finder optical system may be a condenser lens or an ocular lens.

Abstract: An exposure control device for a photographic camera uses a conventional exchangeable lens and achieves a highly accurate exposure control commensurate with a pre-selected shutter speed by a light measuring device measuring scene light transmitted through the objective lens, diaphragm, and exchangeable lens. The device also permits exposure control commensurate with a pre-adjusted diaphragm aperture by storing the output from the light measuring device determined with the adjusted diaphragm aperture to control the shutter speed.

Abstract: An exposure control device for a photographic camera uses a conventional exchangeable lens and achieves a highly accurate exposure control commensurate with a pre-selected shutter speed by a light measuring device measuring scene light transmitted through the objective lens, diaphragm, and exchangeable lens. The device also permits exposure control commensurate with a pre-adjusted diaphragm aperture by storing the output from the light measuring device determined with the adjusted diaphragm aperture to control the shutter speed.

Abstract: In a photographic camera which controls a diaphragm aperture to an optimum aperture automatically, wherein the light from a photographic object which has been transmitted through an objective lens and a diaphragm aperture is measured by means of a light measuring device, as the diaphragm aperture for the objective lens, in its fully open condition is being stopped down from its fully open condition in association with the releasing operation of a shutter, the stop-down operation of the diaphragm aperture then being interrupted when the light measuring output becomes coincident with a value corresponding to a predetermined shutter speed, an improved automatic diaphragm aperture control device in which the movement of an interlocking pin for the objective lens in association with the operation of a diaphragm ring is transmitted to an operating lever within the body of a camera, which lever cooperates with the aforesaid operation of the diaphragm ring through the medium of a movement-enlarging mechanism which is

Abstract: A single lens reflex camera includes an interchangeable objective lens provided with a diaphragm adjusting ring having a drive element and an interchangeable view finder unit housing a light responsive exposure determining means including a follower movable with a varying parameter of the means between a retracted position and a resiliently urged advanced position. A blocking element is normally locked in a position projecting from the unit and preventing the mounting of the finder, and when the follower is released, the blocking element is retractable. The follower is locked in its retracted position and when the finder is mounted the follower is released for movement into operative engagement with the drive element.