FISHEYE LENS

PROBLEM TO BE SOLVED: To sufficiently secure back-focal distance and to excellently compensate magnification chromatic aberration and the curvature of field at the periphery part of an image plane by constituting the lens of a front group for diverging action, a middle group for converging action and a rear group for converging action and making the lens satisfy specified conditional expressions. SOLUTION: This lens system is constituted of the front group for the diverging action, which includes plural negative lenses and a positive lens and has at least a pair of combined lenses, the middle group for the converging action, which includes at least one negative lens and a positive lens, the rear group for the converging action, which includes plural positive lenses and a negative lens and has at least a pair of combined lenses and a diaphragm put between the middle and the rear groups. Then, it satisfies the respective conditions (1) 0.5