| 摘要 |
A telephoto lens system that adopts an inner focusing method and that is capable of satisfactory correction of aberrations while insuring an adequate back focus without increasing the overall lens length. The present telephoto lens system comprises, in order from the object side, a positive first lens group, a negative second lens group and a positive third lens group. The system can be focused on a close-up object by moving the second lens group toward the image. The first lens group comprises a positive first sub-group 1a and a positive second sub-group 1b separated from the first sub-group airspace. The system satisfies the following conditions: (1) 1.4<f/f1<2.0 (2) -3.5<f/f2<-2.5 (3) 0.4<f/f1b<1.0 (4) 0.1<d1ab/f1<0.3 where f is the focal length of the overall system; f1 is the focal length of the first lens group; f2 is the focal length of the second lens group; f1b is the focal length of the sub-group 1b; and d1ab is the distance between the sub-groups 1a and 1b.
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