Patent ID: 8411368

Claim:
A zoom lens system comprising a plurality of lens units and an aperture diaphragm arranged in the lens units, and performing zooming by changing intervals among the lens units, wherein the plurality of lens units, in order from an object side to an image side, includes: a first lens unit having negative optical power; a second lens unit having positive optical power; a third lens unit having positive optical power; and a fourth lens unit having negative optical power, the fourth lens unit moves to the image side along an optical axis at the time of focusing from an infinity in-focus condition to a close-point in-focus condition, and the zoom lens unit satisfies the following condition: −0.1 <f W /f 4 <−0.05 (4) where, f 4 is a focal length of the fourth lens unit, and f w is a focal length of an entire system at a wide-angle limit.