SUPER-WIDE-ANGLE LENS SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a small super-wide-angle lens system suitable to use in a medium film size camera having F-numbers around 4 to 4.5 and a half viewing angle of about 52 degrees. SOLUTION: The small super-wide-angle lens system is composed of a front lens group of positive or negative power, a diaphragm, and a rear lens group of positive power which is the focusing lens group, all of which are arranged in this order from the object side. The front lens group has a first (a) lens group of negative power and a first b lens group of positive power. The first (a) lens group is composed of a first negative meniscus lens with its convex surface facing the object side, a second negative meniscus lens with its convex surface facing the object side, a third positive lens, and a fourth negative lens, all of which are arranged in this order from the object side, and satisfy following conditional expression (1) and (2). Conditional expression (1) f/¾fF¾<0.45. Conditional expression (2) 0.9