Patent ID: 8243370

Claim:
A zoom lens comprising in order from an object side to an image side: a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; and a third lens unit having a positive refractive power, wherein distances between the first to third lens units in a direction of an optical axis are varied during zooming, wherein the second lens unit includes a lens element whose image side surface has a concave shape, a most object side positive lens element and a most image side positive lens element, and wherein the following conditions are satisfied: 0.4 <d 2 a/D 2<0.7 0.5 <f 21/ f 2<1.3 3.2<(β2 T·β 3 W )/(β2 W·β 3 T )<5.0 where D 2 represents a thickness of the second lens unit on the optical axis, d 2 a represents a distance on the optical axis from a surface Rc whose curvature is strongest among those of image side surfaces having concave shapes in the second lens unit to an image side surface of the most image side positive lens element in the second lens unit, f 2 represents a focal length of the second lens unit, f 21 represents a focal length of the most object side positive lens element in the second lens unit, β 2 T and β 3 T respectively represent image-forming magnifications of the second and third lens units at a telephoto end, and β 2 W and β 3 W respectively represent image-forming magnifications of the second and third lens units at a wide-angle end.