Patent ID: 7477457

Claim:
A zoom lens system comprising, in order from an object side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; and a third lens unit having a positive refractive power, during zooming from a wide-angle end to a telephoto end, a space between the first lens unit and the second lens unit and a space between the second lens unit and the third lens unit being changed, the space between the first lens unit and the second lens unit being enlarged in the telephoto end as compared with the wide-angle end, the space between the second lens unit and the third lens unit being narrowed in the telephoto end as compared with the wide-angle end, the zoom lens system further comprising: an aperture stop disposed at a constant relative position with respect to the third lens unit during the zooming, the first lens unit comprising a positive lens, the total number of the lenses of the first lens unit being two or less, the second lens unit comprising, in order from the object side, an object-side negative lens whose concave surface faces an image side, a positive lens and an image-side negative lens, the total number of the lenses of the second lens unit being three, the object-side negative lens and the positive lens of the second lens unit being arranged with an air space on an optical axis therebetween, the following condition being satisfied: −1.70< R 2nlr /f 2 <−0.70 (1A), in which R 2nlr is a paraxial radius of curvature of an image-side surface of the object-side negative lens of the second lens unit, and f 2 is a focal length of the second lens unit.