Patent ID: 7852567

Claim:
A zoom lens system comprises a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, in this order from an object, wherein upon zooming from the short focal length extremity to the long focal length extremity, said positive first lens group, said negative second lens group, said positive third lens group and said positive fourth lens group move along the optical axis of said zoom lens system in a manner so that the distance between said positive first lens group and said negative second lens group increases, the distance between said negative second lens group and said positive third lens group decreases, and the distance between said positive third lens group and said positive fourth lens group increases; and wherein said zoom lens system satisfies the following condition: 13.50< f 1/ fw< 19.50 wherein f 1 designates the focal length of said positive first lens group; and fw designates the focal length of the entire zoom lens system at the short focal length extremity.