Patent ID: 8009367

Claim:
A zoom lens system, in order from an object side to an image side along an optical axis thereof, comprising: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; and a fourth lens group having positive refractive power; wherein, during zooming from a wide-angle end to a telephoto end, both the first and third lens groups move to the object side, and the second lens group first moves to the image side and then moves to the object side, whereby a first variable distance between the first and second lens groups is increased and a second variable distance between the second and third lens groups is decreased; wherein the fourth lens group is also movable along the optical axis to change a third variable distance between the third and fourth lens groups; and wherein each of the third and fourth lens groups includes at least one aspheric surface; the zoom lens system satisfying the following condition: 1.78 <EFL /( fG 2 +fG 3)<14.58 where fG 2 represents an effective focal length of the second lens group, fG 3 represents an effective focal length of the third lens group and EFL represents an effective focal length of the zoom lens system inclusive of the range from the wide-angle end to telephoto end.