Patent ID: 8068281

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; and at least two subsequent lens units,wherein at the time of zooming, all lens units move in a direction along the optical axis so that intervals between the lens units vary, at the time of focusing, a second most image-side lens unit is a focusing lens unit and moves in direction along the optical axis, and a lens unit arranged just on the object side relative to the focusing lens unit has positive optical power, wherein 0.10 mm −1 <|f BAK /f F |/f W <15.0 mm −1 (2) f T /f W >4 where, f BAK is a composite focal length of the lens units arranged on the image side relative to the focusing lens unit at a wide-angle limit, f F is a focal length of the focusing 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.