| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens system whose zooming ratio is >=3.5 and whose front lens diameter is as small as that of a two-group zoom lens, as for a three-group zoom lens which is constituted of negative, positive and negative lens groups in order from an object side. SOLUTION: As for the zoom lens system, the synthesized power of the 1st negative lens group and the 2nd positive lens group is positive, and at zooming from a short focal distance end to a long focal distance end, the 1st to 3rd lens groups are monotonously moved from an image side to the object side, and the following conditional expressions (1) to (3) are satisfied; (1) 0.01<(Δd12W-Δd12T)/fW<0.1, (2) 3.5<fT/f12W<6.0, (3) 4.0<fT/|f3G|<8.0, provided thatΔd12W andΔd12T denote each distance between the 1st lens group and the 2nd lens group at the short focal distance end and the long focal distance end, fW and fT denote each focal distance of the whole system at the short focal distance end and the long focal distance end, f12W denotes the synthesized focal distance of the 1st lens group and the 2nd lens group and f3G denotes the focal distance of the 3rd lens group.
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