PURPOSE: To obtain a long back-focal distance photographing lens properly corrected for aberrations and having good optical performance by specifying the form and constitution of lenses of a front group and rear group.

CONSTITUTION: The lens system is basically constituted of a front group I consisting of a first lens and a third lens with a diaphragm between and having negative refracting power as a whole and a rear group II consisting of a fourth lens to the eighth lens and having positive refracting power as a whole and constituted to form inverted telephoto type. Each lens constitution satisfies the condition of an inequality A when the focal distance of the whole system is (f), the radius of curvature of lens surface of the object side and image face side of the i-th lens are Ri, o, Ri, I, the distance between a second lens and the third lens is D4, and the distance between the third lens and the fourth lens is D6. Thus, a long back-focal distance photographing lens having standard angle of view of 45° and large aperture ratio of F number 1.4 simple in lens constitution and having good optical performance can be obtained.