Abstract: An objective of the pancratic type includes a varifocal front lens group and a fixed-focus rear lens group, the latter consisting of five air-spaced singlets. The front lens group is constituted by a positive first component consisting of three singlets, an axially shiftable negative second component consisting of a singlet and a doublet, and an axially shiftable positive third component in the form of a nearly planoconvex singlet of low power.

Abstract: A projector for motion pictures or slides has a varifocal objective with a positive front component, an axially slidable negative intermediate component and a fixed positive rear lens group. The front component, or at least its foremost lens member, has a lens mount which is displaceable along a track substantially transverse to the optical axis; the track may be curved with its convex side facing the projection screen. A diaphragm just behind the front component has an aperture barely exceeding the diameter of the intermediate component whereas the front component (or its transversely displaceable part) is radially extended past the diaphragm aperture so as to register with it in every position.

Abstract: A zoom objective with a varifocal ratio close to 2:1, particularly for a projector, has a stationary positive front component, a single axially shiftable negative lens and a stationary multilens rear component. An object-side positive lens member of the rear component, adjoining the shiftable negative lens, has a focal length smaller than that of the group constituted by the remaining, image-side lens members of this component. The negatively refracting third member of the rear component may be a doublet with a positively refracting cemented surface, convex toward the image side, or an equivalent lens pair separated by a small air gap.

Abstract: A substantially afocal front attachment of variable magnification ratio, to be combined with a fixed-focus rear lens group in order to form a zoom objective, consists of two fixedly interconnected outer lens members and an axially shiftable biconvex intermediate lens member. The two outer lens members are negative menisci turning their convex sides toward the intermediate lens member. The objective has a varifocal ratio close to 2:1.

Abstract: A varifocal forward lens group of a camera objective, with a pair of axially shiftable negative components bracketed by a pair of substantially fixed positive components, has its negative third component more widely separated from its positive fourth component in a wide-angle position of minimum overall focal length than in a telephoto position of maximum overall focal length. The effective diameter of that third component is just large enough to let a bundle of axially incident light rays fully illuminate the fourth component in the wide-angle position, with less than full illumination in the telephoto position. The positive first component is also just large enough to provide full illumination of the effective area of the third component by axial rays in the telephoto position.

Abstract: A zoom objective is disclosed which consists of a varifocal front lens group and a fixed rear lens group, the front lens group comprising a stationary first component of positive refractivity, axially shiftable second and third components of negative refractivity, and a stationary fourth component of positive refractivity separated from the rear lens group by a reflex prism adjoining a diaphragm space. The assembly of third and fourth components, prism and rear lens group can be selectively combined with various first and second components to provide zoom objectives of different varifocal ratios.

Abstract: A camera of the reflex type comprises a view finder with an achromatic finder objective, an eyepiece, and an interposed inverting lens group. The finder objective includes a negative-meniscus lens of relatively low Abbe number and a biconvex lens of relatively high Abbe number. The negative-meniscus lens, which has a concave forward surface, may be air-spaced from the biconvex lens or may be cemented thereto to form a doublet; in the latter instance the doublet is preceded by a positive, biconvex or planoconvex, front lens.

Abstract: A pancratic wide-angle objective comprises a stationary negative front component in the form of a single meniscus with a convex forward surface, an axially movable intermediate component consisting of a biconvex lens, and a stationary multilens positive rear component separated from the front component by an airspace greater than the focal length of the latter. The individual focal lengths of the front, intermediate and rear components have absolute values in a ratio of approximately 4:5:3.

Abstract: A varifocal objective has an axially shiftable positive front component, an axially shiftable negative intermediate component, and a fixed positive rear component or basic lens group. The latter component consists of five closely spaced lens members, all but the second of them singlets and all but the third of them positively refracting. The intermediate component is separated from the rear component by a diaphragm space which in a position of close approach of these components, corresponding to maximum focal length, is still substantially greater than any air space between the lens members of the rear component. With a varifocal ratio close to 3:1, the distance between the front and rear components is the same in the positions of maximum and minimum focal lengths.

Abstract: A main lens unit having a fixed focal length and consisting of a positive lens member is preceded by an afocal forward lens unit having a variable magnification and consisting of a positive forward lens member, a negative intermediate lens member which is axially movable to change the magnification, and a positive rear lens member. The intermediate lens member is arranged to direct divergent bundles of rays to said rear lens member. The rear lens member is arranged to convert said divergent bundles or rays into bundles of rays which are substantially parallel to the optical axis of the lens and to direct them to said main lens unit. The forward lens member is axially movable to control the position of the image plane. The lens is designed to meet the conditionf.sub.min -f.sub.11 < 6ywhere f.sub.min is the smallest focal length of the lens, f.sub.11 the focal length of the intermediate lens member, and 2y the image field diagonal.