GB444226A - Improvements in photographic view finders - Google Patents

Abstract

444,226. View-finders for kinematographic and photographic cameras. HOWSER, H. R., 1604, 19th Street, Washington, U.S.A. March 9, 1935, No. 7454. Convention date, March 15, 1934. [Classes 97 (i) and 98 (i)] A lens system for a photographic camera comprises a view finder portion surrounding and optically coaxial with a central exposure portion. In Figs. 2 and 3 the lens system is mounted on a ring 1 which is secured to the bellows 4 of a reflex camera, and an inner barrel 13 separates the lens systems into a central taking portion E and an outer portion F which is used solely for view finding. The diaphragm 10 controls the aperture of the lens E, and when making the exposure the view finding portion F is covered by a masking device comprising a series of sector-shaped meshing elements 16 which are urged inwards by the limited rotation of a ring 19 which has slotted tangential arms 22 engaging with pins 23 on the elements 16. A bell-crank lever 24 rotates the ring 19, and is controlled through a flexible rod 29 by the reflex mirror of the camera so that when this is moved upwards the bell-crank lever 24 closes the masking elements to cover the lens portion F. Manual actuation, of the masking means is made when desired by a thumb piece 34. In a modification shown in Fig. 4, the leaves 38 of the diaphragm 35<1> are pivoted and extend into the lens portions through the sides of the barrel 36. They are operated by a rotatable ring 41 which is connected to the inner ring 43 of the diaphragm by rods 42. The leaves 38 move when adjusted so that a constant light valve passes through the lens system irrespective of the diaphragm setting. In a kinematographic camera, Fig. 7, the outer portion of the lens system is segregated from the inner exposure lens portion E. It is mounted in a casing 67 which is internally and externally threaded. A light box 58 is provided with slots in its front wall 59 and with a viewing lens 63 and opening 64. A series of openings are provided in the shutter of the camera which coincide with the outer lens portion so that view finding is possible throughout the exposures. A threaded coupling 71 permits relative focusing adjustment of the two lens portions. This principle of segregation of the two lens portions is also applied to a camera with a focal-plane shutter, the view finding light passing at the side of the shutter blind portion. Also in a folding camera, the upper half of the annular shaped view finder portion is in alignment with a semicircular mirror which throws the image upwards into a hinged light shade.