Patent ID: 7382549

Claim:
A four-group zoom lens comprising, in order from an object side thereof, a first lens group of positive refracting power, a second lens group of negative refracting power, a third lens group of positive refracting power and a fourth lens group, wherein: for zooming from a wide-angle end to a telephoto end of the zoom lens, said first lens group, said second lens group, said third lens group and said fourth lens group are each operable to move with a varying space between adjacent lens groups, said second lens group comprises three lenses, said zoom lens further comprises an aperture stop between said second lens group and said third lens group, wherein said aperture stop is positioned nearer to an image side of the zoom lens at the wide-angle end than at the telephoto end, and said zoom lens satisfies the following conditions: 7<(β 2t ·β 3t ·β 4w )/(β 2w ·β 3w ·β 4t )<15 (1) 7<(β 2t ·β 3t )/(β 2w ·β 3w )<15 (2) where: β 2t is a magnification of the second lens group at the telephoto end, β 3t is a magnification of the third lens group at the telephoto end, β 4t is a magnification of the fourth lens group at the telephoto end, β 2w is a magnification of the second lens group at the wide-angle end, β 3w is a magnification of the third lens group at the wide-angle end, and β 4w is a magnification of the fourth lens group at the wide-angle end.