| 摘要 |
In a macro-adapted zoom lens system capable of high zoom ratio and which covers wide angles, there is disclosed a lens system comprising, in order from the object side, a first lens group having a positive focal length, a second lens group having a negative focal length, a third lens group having a positive focal length, and a fourth lens group having a positive focal length, the focal length of the overall system being varied by displacing all of the four lens groups, and when zooming is effected by shifting the system from a wide-angle end to a telephoto end, a distance between the first and second lens groups being increased while a distance between the second and third lens groups and a distance between the third and fourth lens groups are decreased, with the first and fourth lens groups being situated closer to the object at the telephoto end than at the wide-angle end. The focusing is normally achieved by means of the first lens group and, when closeup shooting is to be made at a nearer distance, the first lens group is fixed at the telephoto end but the second lens group is displaced toward the object while at least one of the third and fourth lens groups are displaced independently so as to increase the distance between the third and fourth lens groups.
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