Zoom lens for super-8 film

Claim 1

A zoom lens, which comprises a main lens unit having a fixed focal length and consisting of a positive lens member, and an afocal forward lens unit preceding said main lens unit and having a variable magnification, said forward lens unit consisting of a positive forward lens member, a negative intermediate lens member which is axially movable to change the magnification, and a positive rear lens member, the positive forward lens member of the afocal part consists of a negative meniscue lens element convex towards the front followed by two biconvex lens elements, said negative intermediate lens member consists of a negative meniscue convex toward the front followed by a negative doublet composed of a biconcave lens cemented to a positive lens element, said positive rear lens member consists of a biconvex lens element, said intermediate lens member being arranged to direct divergent bundles of rays to said rear lens member, said rear lens member being arranged to convert said divergent bundles of rays into bundles of rays which are substantially parallel to the optical axis of the lens and to direct them to said rear lens member, said forward lens member being axially movable to control the position of the image plane, and said lens being designed to meet the condition fmin - fII < 6y where fmin is the smallest focal length of the lens, fII the focal length of said intermediate lens member, and 2y the image field diagonal.