Abstract: A photographic lens of continuously variable focal length (i.e., a zoom lens) consisting of four lens groups designated from front to rear as groups A, B, C, and D. Group B has diverging refractive power; the other three have converging power. An iris diaphragm is located between groups B and C. Group C has a focal length which is numerically greater (disregarding difference in sign) than the focal length of group B by a factor not less than 1.42 and not more than 1.73. Lens group D is formed of two parts D.sub.1 and D.sub.2, separated from each other by a clear air space. The first part D.sub.1 has negative power; the second part D.sub.2 has positive power. The focal length of the part D.sub.1 is numerically greater (disregarding the difference in sign) than the focal length of group C by a factor not less than 1.16 and not more than 1.42.

Abstract: A high speed wide angle lens system of the same general kind disclosed in Glatzel, U.S. Pat. No. 3,915,558, but with a slightly larger aperture and with improved image formation. While the lens formation of the U.S. Pat. No. 3,915,558 starts with two negative components, followed by a positive component, a meniscus, two negative components and two positive components in the rear part, the improved performance of the present invention is achieved by such a modification which enforces the positive power of the rear part of the lens. For this purpose the rear part is made to consist of three positive components (VII, VIII, IX) which are designed in such a way that the quotient of the sum of the surface powers of the air lenses between the three rear positive components .SIGMA..phi..sub..delta. divided by the refractive power (.phi..sup.+.sub.

Abstract: A high power objective or lens system of the same general kind as disclosed in Glatzel U.S. Pat. No. 3,915,558, but with a larger aperture and a slightly smaller angular field of view. Rules or conditions are disclosed which, if complied with, will result in a lens with improved image formation. The present lens is particularly suitable for cinematographic purposes.

Abstract: An extremely high speed wide angle objective lens system, wherein a reducing Newtonian finder telescope is arranged in front of an objective lens group which produces a real image on an image plane. Rules or conditions are stated, and several specific examples are given. In many of the examples, the back focus distance is relatively large, thus making the lens system suitable for use with a mirror reflex camera where room is needed for swinging the reflex mirror.

Abstract: A wide angle lens of moderate aperture, similar in general to the lens of Glatzel et al. U.S. Pat. No. 3,833,290, but differing from it and from other similar lenses in the refractive power distribution as between two dispersing components near the front of the lens, and the refractive power distribution as between two air lenses, one formed between the two dispersive components just mentioned and the other formed between the second dispersing component and a next following condensing component. By designing the lens to have the power distribution at these points between certain stated limits, greatly increased performance is achieved, with reduction of specific aberrations of higher order, and with sharpness of distant real points brought extremely close to the ideal Rayleigh limit.

Abstract: An objective of the expanded Tessar type, having five elements constituting four components (two of the elements being cemented to each other to form one component), all of the components being air spaced from each other. The front two components (in the direction from the object or long conjugate side toward the image or short conjugate side) are both positive. Numerical limits or ranges are given, for certain designated features of the lens system. If a lens of this type is so designed that the designated features fall within the specified ranges, improved results are attained.

Abstract: A high power lens for photograhic purposes, having a relatively large angular field. The lens has at least seven air spaced members, at least three of which are behind a central vertex space, those members in front of such space being divided into two groups of at least two members in each group, the front member in each of these two groups having both its front surface and its rear surface convex toward the front or object side. In the rear group behind the central vertex space, there is a negative member followed by two positive or collecting members, the first such positive member being separated from the negative member by an air lens of diverging action. Specific conditional data are given for several examples or embodiments of the invention.