Abstract: A small-sized, large-aperture, wide-angle zoom lens, having three lens groups of negative, positive, and positive refractive power, respectively, in order from the object side, is disclosed. The FNO of the zoom lens remains constant during zooming. The second lens group includes, in order from the object side, a biconvex lens element, a negative lens element having a concave surface on the object side, a positive lens element having a convex surface on the image side, and a biconvex lens element. The first and second lens groups are moved along the optical axis during zooming, and the third lens group is fixed in position during zooming and includes a stop. Specified conditions are preferably satisfied in order to keep the focal length of the zoom lens short, to correct aberrations, and to keep manufacturing of the zoom lens practicable. Thus, bright, well-corrected images are obtained over the entire range of zoom.

Abstract: A small-sized, large-aperture, wide-angle zoom lens, having three lens groups of negative, positive, and positive refractive power, respectively, in order from the object side, is disclosed. The FNO of the zoom lens remains constant during zooming. The second lens group includes, in order from the object side, a biconvex lens element, a negative lens element having a concave surface on the object side, a positive lens element having a convex surface on the image side, and a biconvex lens element. The first and second lens groups are moved along the optical axis during zooming, and the third lens group is fixed in position during zooming and includes a stop. Specified conditions are preferably satisfied in order to keep the focal length of the zoom lens short, to correct aberrations, and to keep manufacturing of the zoom lens practicable. Thus, bright, well-corrected images are obtained over the entire range of zoom.

Abstract: A zoom lens having three lens groups of positive, positive, and negative refractive power, in order from the object side. A diaphragm is positioned between the first and second lens groups. When zooming from the wide-angle end to the telephoto end, the diaphragm and the third lens group are moved as a unit while the spacing between the first lens group and the diaphragm increases, the spacing between the diaphragm and the second lens group increases, and the spacing between the second lens group and the third lens group decreases. Further, the zoom lens is constructed so as to satisfy the following condition-0.75<R.sub.G21 /f.sub.w <-0.23where R.sub.G21 is the radius of curvature of the surface of the second lens group that is nearest the object side, and f.sub.w is the focal length of the zoom lens at the wide-angle end.

Abstract: A zoom lens having three lens groups I, II, and III, in order from the object side, of positive, positive and negative refractive power, respectively, is made to have a simple drive mechanism which shifts the first lens group and the third lens group as one unit when power is varied. A diaphragm 2 is arranged nearest the image-side surface of the first lens group. When shifting from the wide-angle end to the telephoto end, each lens group is shifted so as to increase the spacing between the first lens group and the second lens group and to decrease the spacing between the second lens group and the third lens group. By making one or more surfaces in the second lens group and the third lens group aspheric, the three-group zoom lens can be made compact and various aberrations can be favorably corrected.

Abstract: A three-group zoom lens having positive, positive and negative refractive power, in order from the object side. A diaphragm is positioned between the first and second lens groups and nearest the second lens group. Zooming is performed by changing the spacings between the lens groups such that, when power is varied from the wide-angle end to the telephoto end, the distance between the first lens group G.sub.1 and the second lens group G.sub.2 increases, while the distance between the second lens group and the third lens group G.sub.3 decreases. The second lens group includes, in order from the object side, a meniscus lens element L.sub.4 having negative refractive power with its concave surface on the object side, a biconvex lens element L.sub.5, a negative lens element L.sub.6 and a biconvex lens element L.sub.7.

Abstract: In a zoom lens comprising three lens groups of positive, positive, and negative in which, upon changing power from its wide angle end to telephoto end, all the three lens groups are moved toward the object side while changing distances between the lens groups, so as to attain variable power; each lens form of the first lens group is specified, and predetermined conditional expressions are satisfied, so as to yield optical performances which are satisfactory to professionals and high-standard amateurs. Upon changing the power from the wide angle end to telephoto end, the air gap between the first lens group G.sub.1 and the second lens group G.sub.2 increases, while the air gap between the second lens group G.sub.2 and the third lens group G.sub.3 decreases. Further, this zoom lens satisfies the following conditional expressions (1) to (3):2.2.ltoreq.f.sub.2 /f.sub.1 .ltoreq.6.6 (1)2.2.ltoreq.f.sub.2 /f.sub.w .ltoreq.5.0 (2)-1.1.ltoreq.R.sub.3 /f.sub.w .ltoreq.0.

Abstract: In a compact wide-angle zoom lens having a two-group configuration composed of positive and negative lens groups, each lens is set to have a predetermined form and satisfy a predetermined range of conditional expression, thereby attaining a high brightness at its wide-angle end, a large angle of view, and a small lens thickness at its telephoto end. The first lens group comprises a biconcave negative first lens L.sub.1 ; a cemented lens composed of a negative second lens L.sub.2 and a biconvex positive third lens L.sub.3 ; and a biconvex positive fourth lens L.sub.4. The second lens group comprises a fifth lens L.sub.5 having an aspheric surface; a sixth lens L.sub.6 having a positive meniscus form with a convex surface directed onto the image side; and a seventh lens L.sub.7 having a negative meniscus form with a convex surface directed onto the image side. The zoom lens further satisfies the following conditional expressions:0<(r.sub.3 +r.sub.4)/(r.sub.3 -r.sub.4)<3.5, 0.5<(r.sub.11 +r.sub.12)/(r.

Abstract: While the third lens group is made stationary when varying power, a stop is disposed in the third lens group so as to suppress change in F.sub.NO when varying power. A zoom lens comprises, successively from the object side, a first lens group (G.sub.1) which is negative as a whole, a second lens group (G.sub.2) which is positive as a whole, and a third lens group (G.sub.3) which is negative as a whole. At the time of zooming, the third lens group (G.sub.3) is made stationary while the first lens group (G.sub.1) and the second lens group (G.sub.2) are made movable. As the two lens groups (G.sub.1 and G.sub.2) are moved along the optical axis (X), the focal length (f) of the whole system is changed, while a luminous flux is efficiently focused onto the imaging surface (2). A stop (1) is disposed in the stationary third lens group (G.sub.3). The zoom lens is configured so as to satisfy the following seven conditional expressions:(1) -1.3<G.sub.1 /f.sub.w <-1.0(2) 0.4<G.sub.2 /f.sub.w <0.7(3) -4.

Abstract: In a wide range of photographing from long shot to close-up, high resolving power and high contrast can be obtained in a wide angle lens system. The wide angle lens system comprises, successively from the object side, a negative meniscus first lens (L1), a junction lens composed of a positive second lens (L2) with a convex surface facing the object and a negative third lens (L3) with a concave surface facing the image, a junction lens composed of a biconvex fourth lens (L4) and a biconcave fifth lens (L5), a positive sixth lens (L6) with a convex surface facing the image, and a negative meniscus seventh lens (L7) with a convex lens facing the image. Also, it satisfies the following conditions (1) to (4):(1) -1.95<F.sub.1 /f<-1.05(2) 1.05<f.sub.23 /f<3.60(3) 1.10<f.sub.45 /f<2.16(4) 1.53<(r.sub.11 +r.sub.10)/(r.sub.11 -r.sub.10)<4.

Abstract: A photographic lens system comprises, in order from the object end, a positive power element having a concave image end surface, an element having a concave image end surface, a negative power element, a positive power element, a meniscus element of a positive power having a concave object end surface, and a doublet comprising a negative power element having a concave object end surface and a positive power element having a convex image end surface, and satisfies the following conditions:0.28<f/f4<2.55 (1)0<f/f5<1.80 (2)-1.15<f/f67<0.65 (3)-0.55<(R6-R7)/(R6+R7)<-0.17 (4)0.03<(R10-R11)/(R10+R11)<0.31 (5)-0.45<(R11-R14)/(R11+R14)<0.10 (6).

Abstract: A large aperture retrofocus lens system is composed of first to sixth lenses arranged in this order from the object side. The first lens has a positive refracting power, the second lens has a negative refracting power, the third lens which is a meniscus lens concave toward the object side, the fourth lens has a negative refracting power, the fifth lens has a positive refracting power and the sixth lens has a positive refracting power.