Abstract: A zoom lens system comprises from the object side, a front lens group having a refractive power of a predetermined sign and a rear lens group having a refractive power of different sign from that of the front lens group. The front lens group is shiftable along the optical axis of the lens system in a zooming operation, and movable perpendicularly to the optical axis for decreasing a blur caused by a hand shake. The rear lens group is shiftable along the optical axis in the zooming operation.

Abstract: A compact-size, light-weight, low-cost zoom lens system with high optical quality is achieved by using a ray restrictor placed at the most object side of the zoom lens system. In one type, the ray resistor shifts toward the object at a speed different from that of the most object side lens of the zoom lens system as the zoom lens system is zoomed toward the longest focal length, which effectively blocks harmful rays causing coma flare in the peripheral area. In another type, the aperture diameter of the ray restrictor varies according to a zooming operation. The ray restrictor of any type is especially effective when used in a zoom lens system composed of two lens groups. By introducing one or more aspherical surfaces satisfying a certain condition (or conditions) in the zoom lens system, various aberrations are further favorably corrected.