Patent ID: 6975461

Claim:
A zoom lens system comprising a positive first lens group that is movable, a negative second lens group that is movable, a positive third lens group that is movable, and positive fourth lens group which is movable or stationary, in this order from an object, wherein upon zooming from the short focal length extremity to the long focal length extremity, the distance between said positive first lens group and said negative second lens group is increased; the distance between said negative second lens group and said positive third lens group is decreased; and the distance between said positive third lens group and said positive fourth lens group is increased; and wherein said zoom lens system satisfies the following conditions: 0.5 <|f 2 |/ f 3 ≦0.745( f 2 <0) 2 <m 3 t/m 3 w ≦2.815 wherein fi designates the focal length of the ith lens group (i=1~3); m 3 t designates the paraxial lateral magnification of said positive third lens group at the long focal length extremity when said object at infinity is in an in-focus state; and m 3 w designates the paraxial lateral magnification of the positive third lens group at the short focal length extremity when said object at infinity is in an in-focus state.