Patent ID: 8659836

Claim:
A zoom lens system, in order from an object side to an image side, comprising 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 the first lens unit is composed of at least three lens elements, the first lens unit has at least one lens element having positive optical power, the first lens unit moves along an optical axis in zooming from a wide-angle limit to a telephoto limit at the time of image taking, and the following conditions (2) and (4) are satisfied: 1.5 <f p /f W <4.0 (2) 0.30 <d 1 /f W <0.85 (4) where f p is a focal length of the lens element having the highest refractive index among the lens elements having positive optical power in the first lens unit, d 1 is an optical axial thickness of the first lens unit, and f W is a focal length of the entire system at a wide-angle limit.