Abstract: A telephoto zoom lens system of a four-group composition that is capable of producing a high zoom ratio without increasing the complexity of a diaphragm stop mechanism and which yet is made compact in structure without sacrificing performance. The telephoto zoom lens system is composed, in order from the object side, of a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power together with a diaphragm stop provided for adjusting the quantity of light admitted, and a fourth lens group having a positive refractive power which consists of lens unit IVA having a positive refractive power and lens unit IVB having a negative refractive power. This lens system performs zooming by moving the first, second and fourth lens groups along the optical axis with the third lens group being fixed and performs focusing by moving the first lens group along the optical axis.

Abstract: A wide-angle reading lens system is disclosed which comprises, in order from the object side, a first lens element which is a negative meniscus lens having its convex surface directed toward the object side, a second lens element which is a positive lens having a strong convex surface directed toward the object side, a third lens element which is a negative lens, and a fourth lens element which is a positive lens having an strong convex surface directed toward the image side, said lens system satisfying the following conditions:-2/0f.ltoreq.f.sub.1 .ltoreq.-0.75f (1) ##EQU1##d.sub.1-7 .ltoreq.0.85f (3)where f denotes the overall focal length of the system; f.sub.1 is the focal length of the first lens element; n.sub.i is the refractive index of an ith lens at the d-line; .nu..sub.i is the abbe number of the ith lens; and d.sub.1-7 signifies the distance from the surface of the first lens element on the object side to the surface of the fourth lens element on the image side.

Abstract: A wide-angle lens system of the seven-unit-seven-element configuration. Arranged in ordered from the object side are two opposed negative meniscus lenses, two opposed positive lenses, a negative lens and two lens with opposed convex surfaces. Four required and one optional numerical conditions are imposed on the focal length, radius of curvature, Abbe numbers and refractive indices.