| 摘要 |
The system has a first positive lens group, and a second negative lens group, arranged in sequence and observable from the object side. A central or rear part of the positive first lens group (11) is formed as a sharp adjustment lens group (11F), which is movable along the optical axis, without on enacting the sharp adjustment altering the distance between the furthest object-side lens surface of the first positive lens group (11) and the picture plane. In the arrangement 0.5 is less than f1G/fF, which is less than 1.2, where f1G is the focus of the positive first lens group, and fF is the focus of the sharp adjustment lens group provided in the positive first lens group.
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