Abstract: A zoom lens system with an improved focusing system is provided. The zoom lens system comprises, from the object to the image side, a front lens group, a zooming lens group including at least a movable lens group, and a macroscopically fixed rear lens group including an aperture stop located inclining towards the object side and a focusing lens group movable on the image side of the aperture stop, wherein the lens system fulfills the following condition: ##EQU1## wherein, f.sub.F represents the focal length of the focusing lens group in the rear lens group, f.sub.III represents the focal length of the whole rear lens group upon infinity focusing, and .gamma. represents the zoom ratio of the zoom lens system.

Abstract: A wide angle zoom lens system for use with a 35 mm single lens reflex camera is provided. The zoom lens system is relatively compact and includes two lens groups that can be relatively displaced along the optical axis to provide variation in focal length as desired. The first lens group has a negative refractive power and the image side second lens group has a positive refractive power. The relationship of their refractive powers has been selected to provide adequate correction of aberrations while maintaining the size, weight and compactness required in a modern zoom lens system with wide angle capability.