Patent ID: 8194317

Claim:
A zoom lens system, in order from an object side to an image side, comprising: a first lens unit having positive optical power; a second lens unit having negative optical power; a third lens unit having negative optical power; a fourth lens unit; and a fifth lens unit, wherein at the time of zooming, all lens units move in a direction along an optical axis so that intervals between the lens units vary, at the time of focusing, either a part of the fifth lens unit or an entirety of the fifth lens unit is a focusing lens unit and moves in a direction along the optical axis, and the focusing lens unit has negative optical power, wherein the third lens unit is an image blur compensation lens unit and moves in a direction perpendicular to the optical axis at the time of compensating image blur caused by vibration in the zoom lens system, and the zoom lens system satisfies the following condition: 0.5 <|f o /f W |<2.8 (2) f T /f W >4 where, f o is a focal length of the image blur compensation lens unit, f T is a focal length of the zoom lens system at a telephoto limit, and f W is a focal length of the zoom lens system at a wide-angle limit.