GB891527A - Photographic objective - Google Patents

Abstract

891,527. Photographic objectives. AGFA A.G. Oct. 7, 1958 [Oct. 26, 1957], No. 32021/58. Class 97(1). In a four component photographic objective having an aperture of at least f/2 and of which the two outer are positive single lenses and the two inner are cemented meniscus negative components concave towards a diaphragm therebetween, the sum of the absolute values of the radii of the surfaces bounding the diaphragm space is greater than 0.5 times the focal length f, the effective diameter of the front lens is greater the diameter of a corresponding lens of relative aperture f/1.4, the diameter of the rear lens is not greater than 0.42 f, the thickness of the front lens is between 1.5 and 3 times the thickness of the rear lens, the radius of the cemented surface of the negative component at the front of the diaphragm space is between the radius of the rear surface of that component and twice the sum of the radii of the front and rear surfaces of that component, and the diaphragm space is less than 1.6 times the sum of the thicknesses of the front and rear lenses. This lens is designed so that with a focal length of about 50 mm. the image completely covers the customary miniature picture size 24 X 36 mm. with a pivoted plate shutter, having maximum opening 22.5 mm., between the objective and the film plane. The objective has a maximum back focal length of 0.67 f. Optical data are given for one example of the objective shown.