Patent ID: 8503101

Claim:
A zoom lens comprising, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power; and a fourth lens unit having a positive refractive power, wherein the second and fourth lens units move during zooming, wherein the first and third lens units do not move for zooming, and wherein the following conditions are satisfied: 12.0 <f 1 /fw< 28.0 −0.265 <f 2/√( fw·ft )<−0.20 5.9 <f 4 /fw< 12.0 where fw denotes a focal length of the entire zoom lens at a wide-angle end, ft denotes a focal length of the entire zoom lens at a telephoto end, f 1 denotes a focal length of the first lens unit, f 2 denotes a focal length of the second lens unit, and f 4 denotes a focal length of the fourth lens unit.