Patent ID: 8810918

Claim:
In a large-aperture zoom lens that comprises the foremost or first lens group of positive refractive power, the second or second foremost lens group of negative refractive power, the third lens group of positive refractive power, and the rearmost or fourth lens group of positive refractive power, all arranged in this sequence from the closest to an object to the closest to an imaging plane, and that permits the magnification power to vary by varying clearances between adjacent ones of the first lens group to the fourth lens group, part of lens pieces in the third lens group is moved in directions orthogonal to the optical axis to compensate for image blur due to hands' tremor, the zoom lens meeting the requirements as defined in the following formula: 0.7<( F 12 W×F 12 T )/( F 34 W×F 34 T )<1.1 where F12W is a composite focal length of the first and second lens groups at the wide-angle end, F34W is the composite focal length of the third and fourth lens groups at the wide-angle end, F12T is the composite focal length of the first and second lens groups at the telephoto end, and F34T is the composite focal length of the third and fourth lens groups at the telephoto end.