Patent ID: 8767311

Claim:
A zoom lens system comprising, in order from an object side to an image side: a first lens group with negative refractive power; a second lens group with positive refractive power; a third lens group with positive refractive power; and a fourth lens group with negative refractive power, wherein, in performing a zooming operation from a wide angle end position to a telephoto end position, the first lens group keeps still, a distance between the first lens group and the second lens groups decreases, a distance between the second lens group and the third lens groups increases, and a distance between the third lens group and the fourth lens group decreases, and wherein the following condition is satisfied: −2.5 <fl /√( fw·ft )<−0.5 where fl denotes a focal length of the first lens group, and fw and ft denote focal lengths of the zoom lens system as a whole in the wide angle end position and in the telephoto end position, respectively.