Patent ID: 7471460

Claim:
A zoom lens system comprising in order from an object side to an image side: a first lens unit having positive optical power, the first lens unit moving so as to be closer to an object at a telephoto end than at a wide-angle end during zooming; a second lens unit having negative optical power, the second lens unit moving during zooming; a third lens unit having positive optical power, the third lens unit moving during zooming; and a fourth lens unit having positive optical power, the fourth lens unit moving in a locus convex toward the object side during zooming, wherein the zoom lens system satisfies the following conditions: 0.5<(β3 t ·β4 w )/(β3 w ·β4 t )<0.9, and 1.2<β4 t /β4 w <1.4, where β 3 w is a lateral magnification of the third lens unit at the wide-angle end, β 4 w is a lateral magnification of the fourth lens unit at the wide-angle end, β 3 t is a lateral magnification of the third lens unit at the telephoto end, and β 4 t is a lateral magnification of the fourth lens unit at the telephoto end.