Patent ID: 8773783

Claim:
An optical system comprising, in order from an object side to an image side, a front unit having a positive refractive power, an aperture diaphragm, and a rear unit, wherein the front unit includes a first lens unit having a positive refractive power, the rear unit includes a second lens unit adjacent to the aperture diaphragm and configured to move in focusing, and the first lens unit includes n (which is an integer equal to or larger than 2) positive lenses and one or more negative lenses, wherein materials of at least two positive lenses of the n positive lenses in the first lens unit satisfy the following conditional expression: 0.0100<ΔθgF where ΔθgF is an abnormal partial dispersion of each material, wherein the material of one or more positive lenses of the n positive lenses in the first lens unit satisfies the following conditional expression: 0.0272<ΔθgF wherein the following conditional expressions are satisfied: 0.15 <Rp/f total<0.90 −15.00 <Rn/f total<−0.15 where Rp denotes a radius of curvature of a refractive surface that is concave and closest to an image in the first lens unit, Rn denotes a radius of curvature of a refractive surface that is concave and closest to an object in the second lens unit, and ftotal is a focal length of an entire optical system.