| 摘要 |
A zoom lens has, in succession from the object side, a first lens group as a convergent focusing group, a second lens group as a divergent magnification changing group, a third lens group as a convergent correcting group, and a fourth lens group as a convergent relay system. The second group and the third group are movable relative to each other along the optical axis to thereby change the magnification while keeping the image plane at a predetermined position. During focusing to objects from infinity to a predetermined short distance, the first group is moved toward the object side and during focusing to an object at a distance still shorter than said predetermined short distance, the first group and the second group are moved along the optical axis at the same time while the third group is maintained at a predetermined position from the image plane.
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