Patent ID: 7075730

Claim:
A zoom lens system, comprising, in order from an object side to an image side: a first lens unit having negative optical power; a second lens unit having positive optical power; a third lens unit having negative optical power; and a fourth lens unit having positive optical power, wherein during zooming from a wide-angle end to a telephoto end, an interval between the first lens unit and the second lens unit reduces, an interval between the second lens unit and the third lens unit increases, and an interval between the third lens unit and the fourth lens unit reduces, and wherein the following conditions are satisfied, 2.9 <bfw/fw <5.0, 3.1 <f 4 /fw <4.5, 0.1 <fw/f 2 <0.42, where bfw represents a back focus of the zooming lens system at the wide-angle end, fw represents a focal length of the zooming lens system at the wide-angle end, and f 2 and f 4 represent a focal length of the second lens unit and a focal length of the fourth lens unit, respectively.