Patent ID: 8599494

Claim:
A zoom lens comprising: a first lens unit with a positive refractive power that does not move for zooming; a second lens unit with a negative refractive power that moves during zooming; a third lens unit that moves during zooming; and a fourth lens unit with a positive refractive power that does not move for zooming, the lens units being arranged along an optical axis of the zoom lens in order from an object plane to an image plane, wherein the first lens unit includes a negative lens element G 1 having a meniscus shape with a convex surface facing towards the object plane, a positive lens element G 2 , a positive lens element G 3 , and a positive lens element G 5 having a meniscus shape with a convex surface facing towards the object plane, the lens elements being arranged in this order from the object plane to the image plane, and wherein, when radii of curvature of object-plane side and image-plane side lens surfaces of the negative lens element G 1 are defined as G 1 R 1 and G 1 R 2 , respectively, a focal length of the negative lens element G 1 is defined as fG 1 , radii of curvature of object-plane side and image-plane side lens surfaces of the positive lens element G 5 are defined as G 5 R 1 and G 5 R 2 , respectively, a focal length of the positive lens element G 5 is defined as fG 5 , and a focal length of the first lens unit is defined as f 1 , then the following conditional expressions are satisfied: −2.2 <fG 1 /f 1<−1.5 1.0<( G 1 R 1 +G 1 R 2)/( G 1 R 1 −G 1 R 2)<2.0 2.4 <fG 5 /f 1<3.7 −4.0<( G 5 R 1 +G 5 R 2)/( G 5 R 1 −G 5 R 2)<−3.0.