| 摘要 |
The invention relates to a zoom optical system that, albeit having high zoom capabilities, has its total length reduced in consideration of size reductions upon received at a lens mount, and an imaging apparatus using the same. The zoom optical system comprises, in order from its object side, a positive first lens group, a negative second lens group, a positive third lens group and a positive fourth lens group. Upon zooming from the wide-angle end to the telephoto end, the second lens group moves in such a way as to lie more on the imaging plane side at the telephoto end than at the wide-angle end, and the third lens group moves. A lens component L<SUB>21 </SUB>having negative refracting power is located in, and nearest to the object side of, the second lens group, and satisfies both condition (1) with respect to its shaping factor and condition (2) with respect to its focal length.
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