Abstract: A Gauss type objective lens system with a high speed of F1.2 for 35 mm SLR cameras is provided. The lens system consists of seven lenses, the object side surface of the second lens being aspheric, and fulfills the following conditions:0.65<Da/Db<1.1B<0 and C<00.55f<R<fwherein: Da represents the sum of axial distance from the object side surface of the second lens to the image side surface of the third lens; Db represents the sum of axial distance from the object side surface of the fourth lens to the image side surface of the fifth lens; B and C represent the aspheric surface coefficients of the fourth degree and of the sixth degree, respectively; f represents the focal length of the whole lens system; and R represents the paraxial radius of curvature of the object side surface of the second lens.

Abstract: A wide angle telephoto type lens system is provided having from object to image side a first positive lens component, a second negative lens component, a third positive lens component, a fourth positive lens component, and a rearmost fifth negative lens component having a concave object side surface and a convex image side surface.

Abstract: An improved tesser type objective lens system having a rear aperture stop with a relatively wide field angle of about 60.degree. and an F-number of about F 2.8 is provided. The thickness of the second negative lens in the lens system is increased relative to the total axial distance of the lens system which permits the reduction of the Petzval sum while maintaining a balance correction of spherical aberration and coma.

Abstract: An improved compact high speed telephoto lens system of a modified Ernostar type is provided, having from the object to the image side of the lens system, a first lens of a positive meniscus shape, convex to the object side; a second lens of a positive meniscus shape, convex to the object side; a third lens of a negative meniscus shape, convex to the object side; a fourth lens of a negative meniscus shape, convex to the object side; and a fifth lens of a positive refractive power. The fourth lens can be a doublet in an alternative embodiment. A positive Petzval sum is provided to insure an appropriate field curvature while permitting the refractive index of the positive lenses to be sufficiently high to correct coma and astigmatism.

Abstract: An improved Gauss type lens system having a relatively large aperture ratio is provided. The lens system comprises seven components between object and image as follows; a first positive meniscus lens element, a second positive meniscus lens element, a third negative meniscus lens element, a fourth meniscus shaped doublet, a fifth positive meniscus lens element, and a sixth positive lens element. The entire lens system is capable of providing a relative aperture of F No. 1.2, an angle of view of 50.degree. and a back focus at least 0.7 times the overall focal length of the lens system.

Abstract: An improved Gauss type lens system having a long back focal length with a relatively high aperture ratio is provided. The Gauss type lens system can comprise a five group, seven lens element system wherein the overall length of the lens system is less than 90 percent of its focal length. The Gauss type lens system has design parameters within the following ranges, wherein the sub-numbers refer to respective lens characteristics, sequentially measured from the object to image side:1.7 < r8/r6 < 1.9, (1)0.9 < r10/r8 < 1.2, (2)0.67 < (d.sub.6 + d.sub.7)/(d.sub.3 + d.sub.4) < 0.87, (3)1.65 <n.sub.2 < 1.72, (4)n.sub.5 > 1.72, n.sub.6 > 1.72 (5)wherein,r represents the radius of curvature;d represents the axial distance, andn represents the refractive index.