A three-group zoom lens includes, in order from the object side, first, second
and third lens groups having negative, positive and positive refractive power,
respectively. During zooming from the wide-angle end to the telephoto end, the
second lens group moves monotonically toward the object side while moving closer
to the first lens group and farther from the third lens group, and the first and
third lens groups reverse directions to define curved paths. The third lens group
is closer to the object side at the wide-angle end and moves toward the object
side for close focusing. The focal lengths of the zoom lens and its lens groups,
the zoom ratio, the length of the zoom lens, and the half-field angle at the wide-angle
end satisfy certain conditions in order to achieve a zoom ratio of at least three
with favorable correction of aberrations.