Patent ID: 8705179

Claim:
A zoom lens system comprising, in order from an object side: a first lens group with positive refractive power; a second lens group with negative refractive power; a third lens group with positive refractive power; a fourth lens group with positive refractive power; and a fifth lens group with positive refractive power, wherein the fifth lens group includes, in order from the object side, a negative biconcave lens and a positive biconvex lens, the negative biconcave lens and the positive biconvex lens being disposed with an air space in between, wherein said airspace is shorter than or equal to a center thickness of the negative biconcave lens and both surfaces of the positive biconvex lens being aspherical, when the zoom lens system zooms from a wide-angle end to a telephoto end, the first lens group does not move, the second lens group, the third lens group, the fourth lens group and the fifth lens group move, and focus adjustments are carried out by the fifth lens group, and a combined focal length f 1 of the first lens group, a combined focal length fw of the zoom lens system at the wide-angle end, a focal length f 51 of the negative biconcave lens in the fifth lens group and a focal length f 52 of the positive biconvex lens in the fifth lens group satisfy conditions given below 13.5< f 1/ fw< 17.5; and 1.0<| f 51/ f 52|<1.5.