Patent ID: 6943961

Claim:
A zoom lens system comprising at least three lens groups, wherein zooming is performed by moving at least two lens groups; wherein a first lens group and a second lens group, in this order from an object, comprise focus-adjusting lens groups that are movable in the optical-axis direction in order not to move a position of an image plane upon zooming, when said zoom lens system is being assembled; and wherein said focus-adjusting lens groups satisfy the following condition: 0.4 <{K 1 ( L )− K 1 ( S )}/{ K 2 ( L )− K 2 ( S )}<1.6 wherein K 1 (L) designates the focus sensitivity of said first lens group at the long focal length extremity; K 1 (S) designates the focus sensitivity of said first lens group at the short focal length extremity; K 2 (L) designates the focus sensitivity of said second lens group at the long focal length extremity; and K 2 (S) designates the focus sensitivity of said second lens group at the short focal length extremity.