| 摘要 |
PROBLEM TO BE SOLVED: To obtain a wide-angle lens system in which change in a short distance is made small, whose image-forming performance is excellent from an infinity object to a short-distance object, which is bright (about F1.8 to 2.0) and whose angle of view is about 35 deg.. SOLUTION: In this retrofocus type wide-angle lens system being negative and positive in order from an object side, a 2nd lens group being positive in constituted of a 2nd F lens group being positive and a 2nd R lens group being positive in order from the object side, and focusing operation is performed by respectively and independently moving an Fa group constituted by integrating a 1st lens group being negative and the 2nd F lens group and an Fb group constituted of the 2nd R lens group. The wide-angle lens system satisfies (1) 0.5<H1/H2R<0.9 (2) 1.7<nPAV and (3) 0.5<Xan/Xbn<1.0; where H1 and H2R indicate the radii of axial luminous flux on the surfaces nearest to the object side of the 1st lens group and the 2nd R lens group at the time of infinity photographing, nPAV indicates the mean value of a refractive index on a d-line of the positive lens in the 2nd lens group and Xan and Xbn indicates the extended amounts of the Fa group and the Fb group from the infinity photographing distance to the shortest photographing distance.
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