Patent ID: 8325427

Claim:
A zoom lens system comprising a negative first lens group, a diaphragm, and a positive second lens group, in that order from the object side, wherein upon zooming from the short focal length extremity to the long focal length extremity, said first lens group and said second lens group move in the optical axis direction while decreasing the distance therebetween, wherein said first lens group includes a negative lens element, a negative lens element and a positive lens element, in that order from the object side, wherein said second lens group includes a positive lens element, a cemented lens that is formed from a positive lens element and a negative lens element, and a positive lens element, in that order from the object side, and wherein the following conditions (1) and (2) are satisfied: 5.2<( d 12 W−d 12 T )/( mT/mW )<7 (1), and 0.3<SF<0.7 (2), wherein d12W designates the distance along the optical axis from the surface closest to the image side of said first lens group to the surface closest to the object side of said second lens group, at the short focal length extremity, d12T designates the distance along the optical axis from the surface closest to the image side of said first lens group to the surface closest to the object side of said second lens group, at the long focal length extremity, mT designates the lateral magnification of said second lens group at the long focal length extremity, mW designates the lateral magnification of said second lens group at the short focal length extremity, SF designates the shape factor of the positive lens element that is provided closest to the object side within the second lens group, SF=( R 2+ R 1)/( R 2− R 1), R2 designates the radius of curvature of the surface on the image side of the positive lens element that is provided closest to the object side within said second lens group, and R1 designates the radius of curvature of the surface on the object side of the positive lens element that is provided closest to the object side within said second lens group.