Patent ID: 8611017

Claim:
A zoom lens system comprising, 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 which are arranged in turn from the object side toward the image side, wherein, in performing a zooming operation from the wide angle end position to the telephoto end position, the first lens group keeps still, the distance between the first and second lens groups becomes small, the distance between the second and third lens groups becomes wide, and the distance between the third and fourth lens groups becomes small; wherein the first lens group is a cemented lens which is formed by joining a first lens element and a second lens element that are arranged in turn from the object side, and the first lens element and the second lens element satisfy the following condition: 70<ν deff <350 where ν deff =1/[f t ·(φ1/νf1+φ2/νf 2)], νf1 denotes the Abbe's number of the first lens element, νf2 denotes the Abbe's number of the second lens element, f t denotes the focal length of the cemented lens, φ1=1/f1 (where f1 denotes the focal length of the first lens element), φ2=1/f2 (where f2 denotes the focal length of the second lens element), and the Abbe's numbers are (nd−1)/(nf-nC).