| 摘要 |
PURPOSE: To obtain a telephoto type three-group zoom lens capable of achieving a zoom ratio being >=4. CONSTITUTION: This zoom lens system is constituted of a 1st negative lens group, a 2nd positive lens group and a 3rd negative lens group in order from an object side, and zooming is performed by moving three lens groups from the 1st one to the 3rd one in an optical axis direction. The 1st lens group is constituted of a doublet which consists of positive and negative lenses and whose surface nearest to the object side is constituted of a concave surface and satisfies following conditional expressions (1) and (2). (1) -1<r1/fW<0 and (2) 1.4<f1G/f1N<1.8. Provided that r1 means the radius of curvature of the surface of the 1st negative lens group nearest to the object side, fW means the focal distance of an entire system at a short focal distance end, f1G means the focal distance of the 1st negative lens group and f1N means the focal distance of the negative lens of the doublet.
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