Patent ID: 8305687

Claim:
A telephoto zoom lens comprising a first lens group having a positive refractive power, a second lens group comprising at least three lenses and having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group, which are sequentially arranged from an object side, wherein: the first lens group comprises a front group which is fixed when focusing and has a positive refractive power, and a rear group which moves when focusing and has a positive refractive power; the entire first lens group comprising the front and rear groups is fixed during zooming, and the second and third lens groups move during zooming; and the second lens group compensates for shaking of an image plane caused by hand-shaking, by moving in a direction perpendicular to an optical axis, and satisfies the following condition: 0.5 <f 2 in/fT< 0.9 wherein f2in denotes the combined focal length of the lenses positioned second and third in the second lens group from the object side, and fT denotes the overall focal length of the telephoto zoom lens at a telephoto position.