ZOOM LENS SYSTEM, INTERCHANGEABLE LENS APPARATUS AND CAMERA SYSTEM

摘要

A zoom lens system, in order from an object side to an image side, comprising: a negative first lens unit; a positive second lens unit; a negative third lens unit; and a positive fourth lens unit, wherein the first, second and third lens units move along an optical axis in zooming, the third lens unit moves along the optical axis in focusing, and the conditions: 2.5≦|(1−(β3T)2)×(β4T)2|≦7.0 and 0.5≦BfW/fW≦4.0 (β3T: a lateral magnification of the third lens unit at an infinite object point distance at the telephoto limit, β4T: a lateral magnification of the fourth lens unit at an infinite object point distance at the telephoto limit, BfW: a back focal length of the zoom lens system at the wide-angle limit, fW: a focal length of the zoom lens system at the wide-angle limit) are satisfied.

主权项

1. A zoom lens system, in order from an object side to an image side, comprising:
a first lens unit having negative optical power; a second lens unit having positive optical power; a third lens unit having negative optical power; and a fourth lens unit having positive optical power, wherein the first lens unit, the second lens unit, and the third lens unit move along an optical axis in zooming from a wide-angle limit to a telephoto limit at a time of image taking, the third lens unit moves along the optical axis in focusing from an infinity in-focus condition to a close-object in-focus condition, and the following conditions (1) and (2) are satisfied:
2.5≦|(1−(β3T)2)×(β4T)2|≦7.0  (1)0.5≦BfW/fW≦4.0  (2) where β3T is a lateral magnification of the third lens unit at an infinite object point distance, at the telephoto limit, β4T is a lateral magnification of the fourth lens unit at an infinite object point distance, at the telephoto limit, BfW is a back focal length of the zoom lens system at the wide-angle limit, and fW is a focal length of the zoom lens system at the wide-angle limit.