Patent ID: 8619372

Claim:
A zoom lens system comprising a front lens group and a rear lens group arranged along an optical axis and in order from an object side, wherein the rear lens group comprises: a first lens unit having a positive refracting power; a second lens unit having a negative refracting power; and a third lens unit having a positive refracting power, wherein upon zooming from a wide-angle end state to a telephoto end state, a space between the front lens group and the first lens unit varies, a space between the first lens unit and the second lens unit increases from d 12 w to d 12 t , and a space between the second lens unit and the third lens unit decreases from d 23 w to d 23 t , wherein the second lens unit comprises the following units arranged in order from the object side: a 2 a partial lens unit having a negative refracting power; and a 2 b partial lens unit having a negative refracting power, wherein either the 2 a partial lens unit or the 2 b partial lens unit is movable so as to have a component in a direction perpendicular to the optical axis, the zoom lens system satisfying conditions of the following expressions: 0.002<( d 12 tâˆ’d 12 w )/ BL< 0.110, and 0.002<( d 23 wâˆ’d 23 t )/ BL< 0.090, where BL=fw 123 Ã—(1âˆ’Î²w 123 ), and where fw 123 is a composite focal length of the first lens unit, the second lens unit, and the third lens unit in the wide-angle end state and Î²w 123 is a composite magnification of the first lens unit, the second lens unit, and the third lens unit in the wide-angle end state.