Patent ID: 8379317

Claim:
A zoom lens system having a plurality of lens units, each lens unit being composed of at least one lens element, the zoom lens system, in order from an object side to an image side, comprising: a front unit having negative optical power as a whole, and including a first lens unit located closest to the object side; and a rear unit having positive optical power as a whole, wherein at least the front unit moves along an optical axis in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit is composed of at most three lens elements, the rear unit includes a lens unit having an aperture diaphragm between lens elements, an air space between which is not varied in zooming, a sub lens unit comprising a part of a lens unit constituting the rear unit moves in a direction perpendicular to the optical axis to optically compensate image blur, and the following conditions (1) and (2) are satisfied: 0.1 <BF/f W <2.0 (1) 0.252 ≦THs/R min <1.00 (2) here, ω W >72°, and FNO W <2.9 where BF is a back focal length of the entire system at a wide-angle limit, f W is a focal length of the entire system at a wide-angle limit, THs is a center-axis interval between the image-side surface of a lens element located nearest the object side of the aperture diaphragm, and the aperture diaphragm itself, R min is the minimum value of the positive radiuses of curvature among the radiuses of curvature of the surfaces having negative optical power within a lens unit that is located nearest the object side of the aperture diaphragm and that moves in zooming from a wide-angle limit to a telephoto limit at the time of image taking, ω W is a view angle at a wide-angle limit, and FNO W is an F-number at a wide-angle limit.