Patent ID: 8305694

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, the positive third lens group having positive power in an entire zooming range of zoom lens system, wherein upon zooming from the short focal length extremity to the long focal length extremity, a distance between said positive first lens group and said negative second lens group increases, and a distance between said negative second lens group and said positive third lens group decreases; wherein said positive third lens group comprises a positive first sub-lens group and a negative second sub-lens group, in this order from the object; wherein said positive first sub-lens group comprises a positive lens element provided at the most object-side thereof and a cemented lens provided at the most image-side thereof; wherein said cemented lens comprises a positive lens element and a negative lens element; and wherein said zoom lens system satisfies the following conditions: 0.3 <f 3 a/f 31<0.6 −0.15 <f 3 a/f 3 PN ≦0.06 wherein f 3 a designates a focal length of said positive first sub-lens group; f 31 designates a focal length of said positive lens element provided at the most object-side of said positive first sub-lens group; and f 3 PN designates a focal length of said cemented lens provided at the most image-side of said positive first sub-lens group.