Patent ID: 8670194

Claim:
A single focal length lens system, in order from an object side to an image side, comprising a front lens unit, an aperture diaphragm, and a rear lens unit composed of a plurality of lens units, wherein the front lens unit includes a negative lens element which has negative optical power and is located closest to the object side, and a positive lens element which has positive optical power and is located on the image side relative to the negative lens element, is composed of three or less lens elements, and does not move along an optical axis but is fixed in focusing from an infinity in-focus condition to a close-object in-focus condition, the rear lens unit includes a focusing lens unit which moves along the optical axis in focusing, and a fixed lens unit which does not move along the optical axis but is fixed in focusing, and the following conditions (1), (2), and (3) are satisfied: 0.4 <f W /f GF <1.5 (1) 0.9< f W /T 1 <4.5 (2) −0.3< f W /f G1 <0.3 (3) where f w is a focal length of the single focal length lens system in an infinity in-focus condition, f GF is a focal length of the focusing lens unit, T 1 is an optical axial distance from an object side lens surface of the negative lens element in the front lens unit to the aperture diaphragm, and f G1 is a focal length of the front lens unit.