| 摘要 |
PROBLEM TO BE SOLVED: To obtain a photographing lens which shows excellent performance to the half angle of view being >=25 deg. in a state where an f-number is about 2.8 in short focal distance and whose back focus is longer than the focal distance by making the lens group of the photographing lens satisfy a specified condition. SOLUTION: This photographing lens is constituted of a 1st lens group 10, a diaphragm S and a 2nd lend group 20 which is positive in order from an object side, and satisfies an expression I;|f/fI|<0.2, and an expression II; 0.7<hI-1 /hI- L<1.0. Provided that (f) is the focal distance of an entire system and (fI) is the focal distance of the 1st lens group 10. hI-1 is the incident height of a paraxial light beam on the 1st surface of the 1st lens group 10, and hI- L is the incident height of the paraxial light beam on the final surface of the 1st lens group 10. The incident height is a distance from an optical axis. Thus, the specified focal length is obtained while securing the long back focus as the entire system.
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