Large aperture ratio photographic lens

Abstract

Disclosed is a photographic lens with improved correction for off-axis halo and image plane distortion, and composed of seven lenses in six components. The first component consists of a positive meniscus lens having a convex surface toward the object, the second component a positive meniscus lens having a convex surface toward the object, the third component a negative meniscus lens having a convex surface toward the object, the fourth component a negative meniscus lens consisting of a negative and a positive lens cemented to each other and having a convex surface toward the image as a whole, the fifth component a positive meniscus lens having a convex surface toward the image and the sixth component a bi-convex lens; with the conditions: (1) 1.75<(N1+N2+N5+N6+N7)/5 (2) (.nu.1+.nu.2+.nu.5+.nu.6+.nu.7)/5>45. (3) 1.85<n6 (4) .nu.4<26. (5) n3<1.67 ##EQU1## (7) 0.30f<D6<0.35f (8) 0.4/f<.vertline..phi.4+.phi.5.vertline.<0.6/f, .phi.4+.phi.5<0 (9) 0.68f<.vertline.R11.vertline.<0.73f, R11<0 wherein: f is the focal length of the whole lens system Ri is the radius of curvature of the i-th surface Di is the distance between the i-th and (i+1)th surface Ni is the refractive index of the i-th lens .nu.i is the Abbe number of the i-th lens .phi.i is the refracting ower of the i-th surface.

Dependencies are inferred from the claim text.