Patent ID: 7777974

Claim:
A lens system comprising, in order from an object: a first lens group; a second lens group; and a third lens group; combined refractive power of the first lens group and the second lens group being positive, the first lens group and the second lens group being movable to an object side for varying focusing from infinity to a close distance, each lens group including at least one positive lens and at least one negative lens, and the following conditional expressions being satisfied: 0.40 <f 12 /f <0.75 2.00 <f 1 /f 2<8.00 where f denotes a focal length of the lens system, f12 denotes a combined focal length of the first lens group and the second lens group upon focusing on the object locating at infinity, f1 denotes a focal length of the first lens group, and f2 denotes a focal length of the second lens group, wherein the third lens group includes, in order from the object, a front lens group having negative refractive power, and a rear lens group having positive refractive power.