| 摘要 |
PROBLEM TO BE SOLVED: To obtain an inexpensive zoom lens system constituting a telephoto type two-group zoom lens system, having about a 35 deg. half field angle and a zoom ratio of about 2.5 at a short facal distance end and reducing the number of constitutional lenses while suppressing the aberrations of respective groups and aberration variation clue to zooming. SOLUTION: In the two-group zoom lens system consisting of positive and negative lens groups arranged successively from the object side, the 1st positive lens group is constituted of a 1st negative lens, a 2nd plastic-made lens forming an aspherical surface at least on one face and a 3rd positive lens and conditional inequalities 3.5<fT/f1 G<4.5, -4.7<fT/F2 G<-3.7 and 63<νd L3 are satisfied. Provided that fT is the focal distance of the whole system at a long focal distance end, f1 G is the focal distance of the 1st positive lens group, f2 G is the focal distance of the 2nd negative lens group, andνd L3 15 the Abbe number of the 3rd positive lens in the 1st lens group.
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