Patent ID: 8593736

Claim:
A zoom lens, comprising, in order from an object side: a first lens unit having a positive refractive power which does not move for varying magnification; a second lens unit having a negative refractive power which moves for varying magnification; a third lens unit having a positive refractive power which moves for varying magnification; and a fourth lens unit having a positive refractive power which does not move for varying magnification, wherein: the first lens unit includes a first sub lens unit which does not move for focusing and a second sub lens unit having a positive refractive power which moves for focusing; the first sub lens unit includes three lenses having negative, positive, and positive refractive powers in order from the object side; and the following conditions are satisfied: 0.5<|( R 12+ R 21)/( R 12− R 21)|<40; and 2.5 <ft/f 1<4.7, where R12 denotes a curvature radius of an image-side surface of a negative lens of the first sub lens unit, R 21 denotes a curvature radius of an object-side surface of an object-side positive lens of the first sub lens unit, f1 denotes a focal length of the first lens unit, and ft denotes a focal length of the zoom lens at a telephoto end thereof.