Telephoto lens system

A telephoto lens system comprising, in order from an object side along an optical axis, a first lens group having a positive refractive power, a second lens group having a smaller refractive power than the first lens group, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power;

• said first lens group comprising a first positive lens element, a second negative lens element and a third positive lens element;
• said second lens group being a cemented lens comprising a fourth negative meniscus lens element and a fifth positive lens element, said cemented surface of said second lens group being convex toward said object;
• said third lens group comprising a sixth positive lens element and a seventh negative lens element;
• wherein focusing is effected by moving said third lens group along said optical axis, said lens system further satisfying the following conditions:
• 0.4f<f.sub.I <0.8f (1)
• .nu..sub.1, .nu..sub.3 >70 (2)
• 0.4f<.vertline.1/.PHI..sub.3 .vertline.<0.7f, .PHI..sub.3 <0 (where .PHI..sub.3 =(n.sub.2 -1)/r.sub.3) (3)
• 0.4f<.vertline.1/.PHI..sub.8 .vertline.<0.6f, .PHI..sub.8 <0 )where .PHI..sub.8 =(n.sub.5 -n.sub.4)/r.sub.8) (4)
• 0.2f<.vertline.f.sub.III .vertline.<0.4f, f.sub.III <0 (5)
• .nu..sub.6 <35, .nu..sub.7 >50 (6)
• where
• f:
• the overall focal length
• f.sub.I :
• the focal length of said first lens group
• f.sub.III :
• the focal length of said third lens group
• n.sub.i :
• the refractive index of an ith lens element at the d-line
• .nu..sub.i :
• the Abbe number of an ith lens element
• r.sub.3 :
• the radius of curvature of a surface of the second lens element on said object side
• r.sub.8 :
• the radius of curvature of said cemented surface in said second lens group
• .PHI..sub. :
• the power of a surface of the second lens element on said object side
• .PHI..sub.8 :
• the power of said cemented surface in said second lens group.