Patent ID: 7184221

Claim:
A zoom lens system comprising, in order from an object side to an image side: a first lens unit with negative refractive power; a second lens unit with positive refractive power; a third lens unit with negative refractive power; a fourth lens unit with positive refractive power; a fifth lens unit with negative refractive power; and a sixth lens unit with positive refractive power, wherein zooming is performed by varying the spacing between the respective lens units so that in comparison to the wide-angle end, the spacing between the first lens unit and the second lens unit becomes smaller, the spacing between the second lens unit and the third lens unit becomes larger, the spacing between the third lens unit and the fourth lens unit becomes smaller, the spacing between the fourth lens unit and the fifth lens unit becomes larger, and the spacing between the fifth lens unit and the sixth lens unit becomes larger at the telephoto end, the fifth lens unit is moved towards the image side in focusing from an infinity object to a close-distance object, and the following condition is satisfied: 1.1<|(1−β5 t 2 )×β rt 2 | where β5t is the lateral magnification at the telephoto end of the fifth lens unit and βrt is the lateral magnification at the telephoto end of an optical part positioned closer to the image side than the fifth lens unit, the optical part including the sixth lens unit.