Optical system, optical apparatus, and method of manufacturing optical system

A method of manufacturing an optical system including a first lens group having positive refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power, arranged in order from an object side, the method comprising:

• disposing each lens within a lens barrel such that
• when focusing, the second lens group moves along an optical axis, and
• the optical system satisfies the following conditional expressions
• 0.100<BFa/f<0.500 and
• −5.000<(−G1R1)/f<500.000
• where BFa is an air equivalent distance on the optical axis from a lens surface on an image side to an image surface for the lens disposed farthest on the image side in the optical system,
• f is a focal length of the optical system, and
• G1R1 is a radius of curvature of the lens surface on the object side for a lens component disposed farthest on the object side in the first lens group.