Patent ID: 8264780

Claim:
A high zoom-ratio 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 the object side, wherein upon zooming from the short focal length extremity to the long focal length extremity, at least the first through third lens groups are moved along the optical axis direction, wherein an amount of movement of said first lens group along the optical axis direction is greater than that of said third lens group, and wherein the following conditions (1), (2) and (3) are satisfied: 0.9 <FT/F 1<2 (1), 3< F 1 /FW< 7 (2), and −8< F 1 /F 2<−5 (3), wherein FT designates the entire focal length of the zoom lens system at the long focal length extremity, F1 designates the focal length of the first lens group, FW designates the entire focal length of the zoom lens system at the short focal length extremity, and F2 designates the focal length of the second lens group.