| 摘要 |
A high zoom-ratio zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group and a positive fourth lens group, in that order from the object side. Upon zooming from the short focal length extremity to the long focal length extremity, at least the first through third lens groups move along the optical axis direction in a manner so that the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the distance between the third lens group and the fourth lens group increases, wherein the amount of movement of the first lens group during zooming is larger than that of the third lens group. The lens element which is provided closest to the object side within third lens group has an aspherical surface formed on each side thereof. The third lens group is an image-shake correction lens group which is moved in a direction orthogonal to the optical axis to change the imaging position in order to correct image shake.
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