Abstract: In a lens barrel for a photographic camera or the like employing operating rings made of synthetic resin, the operating rings are provided with slots on the periphery thereof. The slots are preferably provided to extend in the direction perpendicular to the optical axis of the lens system of the lens barrel.

Abstract: A zoom lens system has a zoom lens holder which varies its length as the focal length is varied. The zoom lens holder includes a fixed ring, an axially movable ring disposed within the fixed ring to which a front lens holder is screwed, and a rotatable cam ring disposed around the fixed ring. The axially movable ring is engaged with the rotatable cam ring by means of a pin fixed to the outer face of the movable ring and slidably engaged with a helical cam groove of the cam ring. The pin radially extends through an axially extending key slot provided in the fixed ring and thereby prevents the movable ring from rotating about the optical axis of the zoom lens system. As the movable ring axially moves, the cam ring is rotated. A rear lens holder is axially movable within the movable ring and is engaged with the cam ring by means of an engaging pin fixed to the rear lens holder and a helical cam groove provided in the cam ring.