| 摘要 |
A zoom lens system is disclosed which is fairly compact and easy to handle despite the fact that it has a constant overall lens length and which allows the first lens group to be moved by a sufficiently small amount during zooming to facilitate the adoption of automatic housing. The zoom lens system includes, in order from the object side, a first lens group having a positive power, a second lens group having a negative power and a third lens group having a positive power, the first lens group being fixed during zooming, the second and third lens groups being moved along the optical axis as zooming is effected, the system satisfying the following conditions (a) and (b): 0.8<fW/f1<1.25 (a) m2 L<-1<m2 S (b) where fW: the focal length of the overall system at the wide-angle end; f1: the focal length of the first lens group; m2L: the magnification by the second lens group at the telephoto end; and m2S: the magnification by the second lens group at the wide-angle end.
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