Patent ID: 7502173

Claim:
A zoom lens system comprising, in order from an object along an optical axis: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; a fourth lens group having positive refractive power; a fifth lens group having positive refractive power; upon zooming from a wide-angle end state to a telephoto end state upon focusing on infinity, the first lens group moves with respect to an image plane, the second lens group moves at first to the image and then to the object, the third lens group moves to the object, and the fourth lens group moves to the object such that a distance between the first lens group and the second lens group increases, a distance between the second lens group and the third lens group decreases, a distance between the third lens group and the fourth lens group varies, and a distance between the fourth lens group and the fifth lens group increases and the following conditional expressions being satisfied: 7.0< f 1/ fW< 12.8 5.8< f 1/(− f 2)<10.0 3.0< f 5/ fW< 10.0 where fW denotes the focal length of the zoom lens system in the wide-angle end state, f 1 denotes the focal length of the first lens group, f 2 denotes the focal length of the second lens group, and f 5 denotes the focal length of the fifth lens group.