Patent ID: 7542215

Claim:
A zoom lens system consisting of, in order from an object: a first lens group having negative refractive power; and a second lens group having positive refractive power; upon varying a focal length from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group decreasing; the first lens group consisting of, in order from the object, a first lens having negative refractive power, and a second lens having positive refractive power, the second lens group consisting of three lenses that are, in order from the object, a third lens having positive refractive power, a fourth lens having negative refractive power and having a convex surface facing the object, and a fifth lens having positive refractive power, the three lenses being disposed without cemented with each other, and the following conditional expression is satisfied: −1.48<( r 2+ r 1)/( r 2 −r 1)<−1.359 where r 1 denotes a radius of curvature of the object side surface of the fourth lens, and r 2 denotes a radius of curvature of the image side surface of the fourth lens.