Patent ID: 8102606

Claim:
A 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; and a third lens unit having a positive refracting power, wherein: at a time of zooming from a wide angle end to a telephoto end, each of spaces between the lens units changes, and the second lens unit comprises a biconcave negative lens which is disposed nearest to the object side, and satisfies the following conditional expressions (1), and the total number of lenses in the second lens unit is not more than three, and the zoom lens system satisfies the following conditional expression (2) −1.0 <SF 2n1 <0.5 (1) 3.0 <f t /f w <12.0 (2) where, SF 2n1 is defined as SF 2n1 =(R 2n1 +R 2n1r )/(R 2n1f −R 2n1r ), when R 2n1f is a paraxial radius of curvature of a surface on the object side, of the negative lens disposed nearest to the object side, in the second lens unit, R 2n1r is a paraxial radius of curvature of a surface on an image side of the negative lens disposed nearest to the object side, in the second lens unit, f w is a focal length of an entire zoom lens system, at the wide angle end, and f t is a focal length of the entire zoom lens system, at the telephoto end, and the first lens unit comprises in order from the object side, a negative lens having a concave surface directed toward an image side, and a biconvex positive lens, and the total number of lenses in the first lens unit is two, and the zoom lens system satisfies the following conditional expressions 1.0 <R 1pr /R 2n1f <5.0 (A), 0.5<SF 1n <30.0 (B), and 0.1 <R 1nr /R 1pf <10.0 (C) where, R 1pr denotes a paraxial radius of curvature of a surface on the image side, of the positive lens in the first lens unit, SF 0.1n is defined as SF 1n =(R 1nf +R 1nr )/(R 1nf −R 1nr ), when R 1nf denotes a paraxial radius of curvature of a surface on the object side, of the negative lens in the first lens unit, R 1nr denotes a paraxial radius of curvature of a surface on the image side, of the negative lens in the first lens unit, and R 1pf denotes a paraxial radius of curvature of a surface on the object side, of the positive lens in the first lens unit.