Patent ID: 8902510

Claim:
A zoom lens system comprising a negative first lens group and a positive second lens group, in that order from an object side, wherein upon zooming from a short focal length extremity of the zoom lens system to a long focal length extremity of the zoom lens system, said first lens group and said second lens group move in an optical axis direction while the distance therebetween mutually decreases, wherein said first lens group consists of a negative lens element, a negative lens element, a negative lens element, and a positive lens element, in that order from the object side; wherein said first lens group comprises a negative first sub-lens group and a positive second sub-lens group, in that order from the object side, wherein said second sub-lens group constitutes a focusing lens group that is moved in the optical axis direction during a focusing operation, wherein said second sub-lens group comprises a positive single lens element, wherein the following condition (1) is satisfied: −0.79 ≦SF≦− 0.47 (1), wherein SF=(br1−br2)/(br1+br2), br1 designates the radius of curvature of the surface on the object side of said positive single lens element of said second sub-lens group, and br2 designates the radius of curvature of the surface on an image side of said positive single lens element of said second sub-lens group, wherein the following condition (2) is satisfied: −4.84 ≦f 1 b/f 1 a≦− 3.59 (2), wherein f1b designates the focal length of said second sub-lens group, and f1a designates the focal length of said first sub-lens group, wherein said first sub-lens group comprises three negative lens elements which each has a concave surface on the image side, and wherein the following condition (3) is satisfied: −3.5 <fL 1/( fL 2 *fL 3) 1/2 ≦−1.17 (3), wherein fL1 designates the focal length of the first negative lens element that is provided within said first sub-lens group, in that order from the object side, fL2 designates the focal length of the second negative lens element that is provided within said first sub-lens group, in that order from the object side, and fL3 designates the focal length of the third negative lens element that is provided within said first sub-lens group, in that order from the object side.