Abstract: A zoom lens comprises a fixed cylinder, an outer movable cylinder, and an inner movable cylinder which is provided in the interior thereof with a shutter and a front group lens. The front group lens is fixed by an outer frame which is fastened with the shutter. The outer frame retains a chain plate capable of being driven by a rotary plate of the shutter. The chain plate has an indicator portion. The inner movable cylinder is provided in the inner wall thereof with a reference indicium, which is level with and aligned with the indicator portion of the chain plate at such time when the zoom lens is located at various focusing positions.

Abstract: A zoom lens is formed of a fixed cylinder, an outer movable cylinder, an inner movable cylinder, and a guide plate disposed between the fixed cylinder and the outer movable cylinder. The outer movable cylinder is movably fitted into the fixed cylinder and is provided at one end thereof with a first locating point, a second locating point, and a third locating point. The guide plate displaces along with the outer movable cylinder and has a reference portion, which is aligned with the first locating point, the second locating point, and the third locating point to determine the focal position of the lens.