Patent ID: 7817347

Claim:
A zoom lens comprising, in order from an object side thereof, a first lens group having positive refracting power, a second lens group having negative refracting power, a third lens group having positive refracting power, and a fourth lens group having positive refracting power, wherein: zooming is implemented by changing a spacing between the respective lens groups; said first lens group consists of, in order from the object side, a negative lens element, and a positive lens element; and the following conditions are satisfied: 5.0 <f t /f w <50.0 (1) 1.4<N d1p <1.7 (2) where f w is a focal length of the whole zoom lens system at a wide-angle end, f t is a focal length of the whole zoom lens system at a telephoto end, and N d1p is the d-line refractive index of the positive lens in said first lens group.