Abstract: A zoom lens system having a positive first lens group and a negative second lens group in this order from the object side, wherein zooming is performed by varying the distance between the first and the second lens groups. The zoom lens system satisfies the following conditions (1) and (2): 1.4<fw/f1G<1.7  (1) 0.85<&Sgr;d1G/fw<1.1  (2) wherein: fw designates the focal length of the zoom lens system at the short focal length extremity; and f1G designates the focal length of the positive first lens group; and &Sgr;d1G designates the thickness of the positive first lens group.

Abstract: A photographing lens includes a front lens unit and a rear lens unit that are arranged in this order from the object side. The front lens unit comprises, in this order from the object side, a first lens element which is a positive meniscus lens having a convex surface facing the object side, a second lens element which is a positive meniscus lens having a convex surface facing the object side and a third lens element that is cemented to the second lens element. The third lens element is a negative meniscus lens having a convex surface facing the object side. The rear lens group comprises, in this order from the object side, a fourth lens element which is a positive meniscus lens having a convex surface facing the image side, a fifth lens element which is a negative meniscus lens having a concave surface facing the object side and a sixth lens element which is cemented to the fifth lens element. The sixth lens element is a positive meniscus lens having a convex surface facing the image side.

Abstract: A photographic lens comprising: a front lens group and a rear lens group that are arranged in order from the object side; wherein the front lens group comprises, in order from the object side, a first lens element which is a positive meniscus lens having a convex surface facing the object side, a second lens element which is a positive meniscus lens having a convex surface facing the object side, and a third lens element that is cemented to the second lens element, the third lens element being a negative meniscus lens having a convex surface facing the object side; wherein said rear lens group comprises, in order from the object side, a fourth lens element which is a positive meniscus lens having a convex surface facing the image side; a fifth lens element which is a negative meniscus lens having a concave surface facing the object side; a sixth lens element that is cemented to the fifth lens element, the sixth lens element being a positive meniscus lens having a convex surface facing the image side; and wher

Abstract: A zoom lens system which includes a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group. All of the lens groups move toward the object upon zooming from the short focal length extremity to the long focal length extremity. The positive third lens group includes at least a positive lens element and a negative lens element. The positive fourth lens group includes at least one negative lens element. When the object distance changes from infinity to a finite object distance, focusing is performed by moving the second lens group toward the object,and the following conditions are satisfied: (1)-1.23<m.sub.3-4W <-1.0, (2)0.02<d.sub.19 /fw<0.30, (3)1.6<n.sub.L13 <1.76; wherein m.sub.3-4W : the resultant lateral magnification of the third and fourth lens groups which are considered to be one lens group at the short focal length extremity; d.sub.

Abstract: A zoom lens system having a negative first lens group and a positive second lens group in this order from the object, each of which is arranged to move for zooming; the first negative lens group including a first single positive lens element, a second single negative meniscus lens element having convex surface facing the object, a third single negative lens element and a fourth a positive single lens element having a convex surface facing the object, in this order from the object; the second positive lens group including a fifth a positive biconvex single lens element, a sixth positive single meniscus lens element having the convex surface facing the object, a seventh negative biconcave single lens element and an eighth positive single lens element, in this order from the object; and the following condition is satisfied:(n.sub.2 +n.sub.3)/Z<1.32 (1)Wherein n.sub.i designates the refractive index of the i-th lens; Z designates the zoom ratio of the zoom lens system.

Abstract: A close-up attachment lens, for enabling close-up photograph along with a main lens, is arranged to be attached to the object side of said main lens. The close-up attachment lens comprises, in that order from the object side, a positive first lens element, a negative second lens element, and a positive third lens element formed as a meniscus lens that is convex on the image side. Furthermore, the close-up attachment lens satisfies the following conditions:0.005<d2/fA<0.040 (1)0.010<(d2+d4)/fA<0.060 (2)wherein:di designates the distance between the ith surface and (i+1).sup.th surface;fA designates the focal length of the attachment lens.

Abstract: The improved zoom lens system comprises, in order from the object side, a positive first lens group, a positive second lens group and a negative third lens group, the third lens group having a biaspheric positive lens element on the side the closest to the object that has a convex surface directed towards the image and the third lens group further including at least one negative lens element that has a concave surface directed towards the object, and the system is further characterized in that all lens groups are moved towards the object during a zoom from the wide-angle end to the narrow-angle end, and the following conditions are satisfied: (a) 0<.DELTA.X.sub.3G1 /fs; (b) -0.75<X.sub.3G2 /.DELTA.X.sub.3G1 <0; (c) -1.5<r.sub.3G2 /fs<-0.5; where .DELTA.X.sub.3G1 : the amount of asphericity of the surface on the object side of the positive lens element on the object side of the third lens group; .DELTA.X.sub.

Abstract: A shiftable lens system having front and rear lens groups, wherein a part or the whole of the rear lens group is shiftable in a direction perpendicular to the principal optical axis thereof.

Abstract: A tilting lens system including a plurality of lens groups in which at least one lens group subsequent to a first lens group can be tilted about a predetermined point on a principal ray axis thereof.

Abstract: A mechanism for adjusting the diopter setting of a finder assembly which has an objective optical system and an eyepiece optical system, includes an object side image forming position adjusting device which adjusts the position where an image is to be formed by the objective optical system. The mechanism effectively compensates for any change that occurs in the position where an image is formed by the objective optical system due to temperature or humidity variations. Thus, the problem of plastic lenses having their focal lengths extended in a hot and humid environment is solved by the invention.

Abstract: A mechanism for adjusting the diopter setting of a finder assembly which has an objective optical system and an eyepiece optical system, includes an object side image forming position adjusting device which adjusts the position where an image is to be formed by the objective optical system. The mechanism effectively compensates for any change that occurs in the position where an image is formed by the objective optical system due to temperature or humidity variations. Thus, the problem of plastic lenses having their focal lengths extended in a hot and humid environment is solved by the invention.

Abstract: A stereoscopic camera is provided with a mechanism to move reflective members into and out of an optical path such that the camera may take stereoscopic photographs in one position of the moving mechanism. The camera may also take normal full-frame photographs in a second position of the moving mechanism.

Abstract: A compact zoom lens has two lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in this order from an object. The second lens group is provided with a first lens made of a positive meniscus lens with a concave surface located adjacent to an object to be photographed, and a second negative lens with a concave surface adjacent to the object. The compact zoom lens satisfies the relationships defined by:(1) 1.9<f.sub.w /r.sub.1(2) 3.4<f.sub.T /f.sub.1 <4, and(3) 0.5<f.sub.T /f.sub.2-1 <1.2,wherein f.sub.w designates the focal length of the whole lens system at a wide-angle extremity, r.sub.1 the radius of curvature of the surface of the first lens, f.sub.T the focal length of the whole lens system at a telephoto extremity, f.sub.1 the focal length of the first lens group, and f.sub.2-1 the focal length of the first lens of the second lens group.

Abstract: A stereo photographing system having a stereo adapter for photographing two separate images of a same subject viewed from different points and formed onto one picture frame next to each other, and a camera including a finder and a photographing lens to which the stereo adapter can be detachably attached at the front end of the photographing lens. The stereo photographing system further includes a finder viewing field determining means provided in an optical path of the finder for selectively determining either a regular viewing field or a stereo viewing field, a detecting means which detects the stereo adapter when the stereo adapter is mounted to the camera, and a switching means which swatches between the regular viewing field and the stereo viewing field determined by the viewing field determining means in accordance with the detecting means.

Abstract: A zoom lens system for a compact camera, having a zoom ratio of approximately 2 or 3 and a smaller overall lens length at the telephoto end than the focal distance at the telephoto end, and which optically experiences only a small focus shift due to environmental changes such as temperature or humidity. The zoom lens system includes a positive lens group and a negative lens group. A positive plastic lens element is disposed in either the positive lens group or the negative lens group. The magnification of the system is adjusted by varying the distance between the positive and negative lens groups. The zoom lens system satisfies the following conditions:0.9<f.sub.t /f.sub.p <1.6 (1)0.6<m.sub.p '-m.sub.p <1.2 (2)2.9<m.sub.MAX <4.0 (3)where f.sub.t is the focal length of the overall system at the telephoto end, f.sub.p is the focal length of the positive plastic lens element, m.sub.

Abstract: An improved zooming viewfinder includes, in order from the object side, a positive first lens group, a negative second lens group that has a zooming capability and which is capable of moving along the optical axis, a negative third lens group that has a half mirror surface on the pupil side, and a fourth lens group that is a positive eyepiece and which has a field-limiting frame on the side the closest to the object. The eyepiece includes, in order from the object side, a positive lens element 4a and a negative lens element 4b.

Abstract: A zoom lens system is disclosed which is fairly compact and easy to handle despite the fact that it has a constant overall lens length and which allows the first lens group to be moved by a sufficiently small amount during zooming to facilitate the adoption of automatic housing. The zoom lens system includes, in order from the object side, a first lens group having a positive power, a second lens group having a negative power and a third lens group having a positive power, the first lens group being fixed during zooming, the second and third lens groups being moved along the optical axis as zooming is effected, the system satisfying the following conditions (a) and (b):0.8<fW/.function.1<1.25 (a)m2 L<-1<m2 S (b)wherefW: the focal length of the overall system at the wide-angle end;.function.1: the focal length of the first lens group;m2L: the magnification by the second lens group at the telephoto end; andm2S: the magnification by the second lens group at the wide-angle end.

Abstract: A telephoto lens system that adopts an inner focusing method and that is capable of satisfactory correction of aberrations while insuring an adequate back focus without increasing the overall lens length. The present telephoto lens system comprises, in order from the object side, a positive first lens group, a negative second lens group and a positive third lens group. The system can be focused on a close-up object by moving the second lens group toward the image. The first lens group comprises a positive first sub-group 1a and a positive second sub-group 1b separated from the first sub-group airspace. The system satisfies the following conditions:(1) 1.4<f/f.sub.1 <2.0(2) -3.5<f/f.sub.2 <-2.5(3) 0.4<f/f.sub.1b <1.0(4) 0.1<d.sub.1ab /f.sub.1 <0.3where f is the focal length of the overall system; f.sub.1 is the focal length of the first lens group; f.sub.2 is the focal length of the second lens group; f.sub.1b is the focal length of the sub-group 1b; and d.sub.

Abstract: A zoom lens system for a compact camera, having a zoom ratio of approximately 2 or 3 and a smaller overall lens length at the telephoto end than the focal distance at the telephoto end, and which optically experiences only a small focus shift due to environmental changes such as temperature or humidity. The zoom lens system includes a positive lens group and a negative lens group. A positive plastic lens element is disposed in either the positive lens group or the negative lens group. The magnification of the system is adjusted by varying the distance between the positive and negative lens groups. The zoom lens system satisfies the following conditions:0.9<f.sub.t /f.sub.p <1.6 (1)0.6<m.sub.p '-m.sub.p <1.2 (2)2.9<m.sub.MAX <4.0 (3)where f.sub.t is the focal length of the overall system at the telephoto end, f.sub.p is the focal length of the positive plastic lens element, m.sub.

Abstract: A zoom lens system for a compact camera, having a zoom ratio of approximately 2 or 3 and a smaller overall lens length at the telephoto end than the focal distance at the telephoto end, and which optically experiences only a small focus shift due to environmental changes such as temperature or humidity. The zoom lens system includes a positive lens group and a negative lens group. A positive plastic lens element is disposed in either the positive lens group or the negative lens group. The magnification of the system is adjusted by varying .?.the.!. .Iadd.a .Iaddend.distance between the positive and negative lens groups. The zoom lens system satisfies the following conditions:0.9<f.sub.t /f.sub.p <1.6 (1)0.6<m.sub.p '-m.sub.p <1.2 (2).?.2.9<.!. .Iadd.3.13.ltoreq..Iaddend.m.sub.MAX <4.0 (3)where f.sub.t is the focal length of the overall system at the telephoto end, f.sub.p is the focal length of the positive plastic lens element, m.sub.