Patent ID: 8223439

Claim:
An optical system comprising, in order from an object side to an image side: a first lens unit; a stop; and a second lens unit, wherein the first lens unit includes: a first negative lens having a meniscus shape and a negative refractive power at a position closest to the object side; and a negative lens Gn having a negative refractive power at a position closer to the image side than the first negative lens, wherein the second lens unit includes a positive lens Gp having a positive refractive power, wherein a material of each of the negative lens Gn and the positive lens Gp satisfies the following condition: θ gF −(−0.001682·ν d+ 0.6438)≧0.01 where “νd” denotes an Abbe number of a lens material and “θgF” denotes a relative partial dispersion with respect to g-line light and F-line light, and wherein an angle (θ) to an optical axis of an off-axis principal ray incident on a lens surface of the first negative lens facing the object side at an arbitrary image height y and a focal length (f) of the entire optical system satisfy the following condition: 1.8≦( y/f sin(θ/2))≦2.1.