Patent ID: 7796344

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 the at least two subsequent lens units include a lens unit A and a lens unit B arranged on the image side relative to the lens unit A, 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, the lens unit A moves in a direction along the optical axis, and the following condition is satisfied: 0.10<| f BAK /f F |/( f T /f W )<15.0 (here, f T /f W >4, ω W <20°) 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 entire system at a telephoto limit, f W is a focal length of the entire system at a wide-angle limit, and ω W is a half view angle at a wide-angle limit.