Patent ID: 7715112

Claim:
A zoom lens system comprising, in order from an object side to an image side: a first lens unit having a positive optical power, the first lens unit including one negative lens element and two positive lens elements; a second lens unit having a negative optical power; a third lens unit having a positive optical power; and a fourth lens unit having a positive optical power, wherein the first lens unit moves during zooming, and wherein the following condition is satisfied: 0.05 <f 1/( st 1 ×ft/fw )<0.2 1.5<β3 T /β3 W< 3.6 where f 1 denotes a focal length of the first lens unit, st 1 denotes a distance between positions of the first lens unit at a wide-angle end and at a telephoto end, fw and ft denote focal lengths of the entire system at the wide-angle end and at the telephoto end, respectively, and β 3 W and β 3 T denote lateral magnifications of the third lens unit at the wide-angle end and at the telephoto end, respectively.