Patent ID: 8159758

Claim:
A zoom lens system comprising: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power; and a fourth lens unit having a positive refractive power, wherein the first, second, third, and fourth lens units are arranged along an optical axis in order from the object side to the image side, and the lens units move along the optical axis from a wide-angle end to a telephoto end such that intervals between adjacent lens units vary during zooming, wherein the first lens unit consists of an first-a lens element having a negative power and a first-b lens element having a positive refractive power, and the second lens unit consists of a second-a lens element having a negative refractive power, a second-b lens element having a negative refractive power, and a second-c lens element having a positive refractive power, and wherein 7.5 <ft/fw< 13.0, n 12>−0.0013ν12+1.63, and ν12>65 are satisfied, where n12 and ν12 respectively represent the refractive index and the Abbe number of the first-b lens element, and fw and ft respectively present the focal length at the wide-angle end and the telephoto end of the zoom lens system.