| 摘要 |
PROBLEM TO BE SOLVED: To obtain an inner focus type compact telephotographic lens whose half viewing angle is about 4 to 8 deg.. SOLUTION: This telephotographic lens is constituted of a 1st positive lens group, a 2nd negative lens group and a 3rd positive lens group in order from an object side, and the 2nd lens group is moved to an image side in the case of focusing from infinity to the shortest photographing distance. The lens satisfies following conditional expressions (1) to (4). (1) 1.35<f/f1<1.80, (2) 1.30<|f/f2|<1.85, (3) 0.48<f/f3<0.75 and (4) 0.10<|L2/f2|<0.22. Provided that f: the focal distance of an entire system, f1: the focal distance of the 1st lens group, f2: the focal distance of the 2nd lens group, f3: the focal distance of the 3rd lens group and L2: a distance between the 2nd and the 3rd lens groups at the time of focusing at infinity.
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