Patent ID: 7253972

Claim:
A telephoto lens system of at least a four-lens-group arrangement comprises a positive first lens group, a positive or negative second lens group, a negative third lens group and a positive fourth lens group, in this order from an object, wherein said telephoto lens system of the at least four-lens-group arrangement comprises six lens elements or less in total; wherein said positive or negative second lens group comprises a positive lens element and a negative lens element that are cemented to each other, in this order from the object; wherein said positive lens element has a convex surface facing toward the object side, said convex surface having a larger curvature than a surface of the positive lens element facing toward the image side; wherein said positive or negative second lens group satisfies the following condition: 0.8< f 2 p/|f 2 n|< 1.4 wherein f 2 p designates the focal length of said positive lens element of said second lens group; and f 2 n designates the focal length of said negative lens element of said second lens group; and wherein the telephoto lens system satisfies the following conditions: 80<ν2 p 20<ν2 p−ν 2 n< 60 wherein ν2p designates the Abbe number of said positive lens element of said positive or negative second lens group; and ν2n designates the Abbe number of said negative lens element of said positive or negative second lens group.