Patent ID: 7433132

Claim:
A zoom lens system which is a four-unit zoom lens system, comprising, in order from an object side: a first lens unit having a positive refracting power; a second lens unit having a negative refracting power; a third lens unit having a positive refracting power; and a fourth lens unit having a positive refracting power, wherein at a time of zooming from a wide angle end to a telephoto end, at least the first lens unit, the second lens unit, and the third lens unit move, and a space between the lens units changes, and a total number of lenses in the second lens unit is not more than three, and the zoom lens system satisfies the following conditional expressions 1.2<(β 2t /β 2w )/(β 3t /β 3w )<6.0 (1A) and 3.0 <f t /f w <20.0 (2A) where, β 2w denotes a lateral magnification of the second lens unit, at a wide angle end, β 2t denotes a lateral magnification of the second lens unit, at a telephoto end, β 3w denotes a lateral magnification of the third lens unit, at the wide angle end, β 3t denotes a lateral magnification of the third lens unit at the telephoto end, f w denotes a focal length of the entire zoom lens system, at the wide angle end, and f t denotes a focal length of the entire zoom lens system at the telephoto end.