| 摘要 |
A zoom lens system that has five lens groups with respectively positive, negative, positive, positive, and positive refractive powers in that order from an object side to an image forming side is provided. The third lens group consists, in order from the object side, of a first positive lens, a negative lens, and a second positive lens, the first positive lens and the negative lens composing a cemented lens. The fourth lens group consists, in order from the object side, of a first positive lens, a negative lens, and a second positive lens, the negative lens and the second positive lens composing a cemented lens. In the zoom lens system, zooming (operation) between a wide-angle end and a telephoto end is carried out without moving the first lens group and the fifth lens group, and focusing is carried out by moving the fifth lens group.
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