Patent ID: 8867145

Claim:
A zoom lens system comprising: in order from an object side to an image side, a first lens unit having positive optical power and composed of not more than two lens elements; a second lens unit having negative optical power; a third lens unit having negative optical power; and a fourth lens unit having positive optical power, wherein in zooming from a wide-angle limit to a telephoto limit, the fourth lens unit moves along an optical axis, and the following conditions are satisfied: 0.2<| f W /f F |<0.6 (3) 1.50<nd 1 <1.72 (9) 50<vd 1 <75 (10) where f W is a focal length of the zoom lens system at a wide-angle limit, f F is a focal length of the third lens unit, nd 1 is a refractive index to the d line of a positive lens element constituting the first lens unit, and vd 1 is an Abbe number of a positive lens element constituting the first lens unit.