Patent ID: 8913328

Claim:
A zoom lens system comprising a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, in that order from an object side, wherein upon zooming from a short focal length extremity to a long focal length extremity, a distance between said first lens group and said second lens group increases, and a distance between said second lens group and said third lens group decreases, wherein said first lens group includes a positive first sub-lens group which remains at a stationary position with respect to an optical axis direction during a focusing operation, and a positive second sub-lens group which moves in the optical axis direction during the focusing operation, in that order from the object side, and wherein the following conditions are satisfied: 0.35< f 1 b/f 1 a< 0.57, and −4.4< f 1 w/f 2<−3.2, wherein f 1 b designates a focal length of said second sub-lens group; f 1 a designates a focal length of said first sub-lens group; f 1 w designates a focal length of said first lens group at the short focal length extremity when said zoom lens system is focused on an object at infinity; and f 2 designates a focal length of said second lens group.