Patent ID: 8786958

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 third lens unit moves along an optical axis in focusing from an infinity in-focus condition to a close-object in-focus condition, and the following conditions (1) and (2) are satisfied: 0.5 <|f 3 /f W |<2.0 (1) 0.005 <d 3 /f W <0.070 (2) where f 3 is a focal length of the third lens unit, d 3 is an optical axial thickness of the third lens unit, and f W is a focal length of the entire system at a wide-angle limit.