Patent ID: 8331034

Claim:
A zoom lens system comprising, in an order from an object side to an image side: a first lens unit having positive refractive power; a second lens unit having negative refractive power; a third lens unit having positive refractive power; a fourth lens unit having negative refractive power; and a fifth lens unit having positive refractive power, wherein in zooming from a wide angle end to a telephoto end, the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit move so that an interval between the first lens unit and the second lens unit is larger at the telephoto end than that at the wide angle end, an interval between the second lens unit and the third lens unit is smaller at the telephoto end than that at the wide angle end, and an interval between the third lens unit and the fourth lens unit varies, wherein the first lens unit moves along a locus convex toward an image plane in zooming, and wherein the following conditional expressions are satisfied: 8.0 <f 1 /fw< 25.0; 0.35 <f 1 /ft< 0.70; and 0.05 <m 1mid/| m 1|<0.60, where f 1 denotes a focal length of the first lens unit, fw and ft denote focal lengths of an entire system at the wide angle end and at the telephoto end, respectively, m 1 denotes a movement amount of the first lens unit accompanying the zooming from the wide angle end to the telephoto end, and m 1 mid denotes a movement amount of the first lens unit from the wide angle end to a zoom position where the first lens unit is positioned closest to the image plane.