Patent ID: 8842371

Claim:
A zoom lens system, comprising, in order from an object side to an image side: a focus lens portion; a zoom portion including a lens unit that moves for zooming; a relay portion that does not move for zooming; and an aperture stop for light amount adjustment disposed between the zoom portion and the relay portion, wherein: the relay portion comprises, in order from the object side to the image side, a first unit having negative optical power, a second unit that can enter into and exit from an optical path, a third unit having positive optical power, and a fourth unit that is inserted in the optical path for shifting a focal length range of an entire system to a long focal length side in a state that the second unit is removed from the optical path; and when a distance on an optical axis between the aperture stop and a last lens surface of the fourth unit in a state in which the fourth unit is inserted in the optical path is denoted by l_out, a distance on the optical axis between a first lens surface and the last lens surface of the fourth unit is denoted by l_ex, and an aperture diameter in an opened state of the aperture stop is denoted by ea_sp, the following expressions are satisfied: 1.25< l _out/ ea — sp< 1.38; and 0.40 <l — ex/l _out<0.55.