Abstract: A zoom lens includes: a first lens group having a negative refractive power; and a second lens group having a positive refractive power, provided in this order from an object side. Magnification is changed by moving the first lens group and the second lens group. The first lens group includes a first lens having a negative refractive power, a second lens, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, provided in this order from the object side. The zoom lens satisfies predetermined conditional formulae.

Abstract: A variable magnification optical system substantially consists of a first lens-group having positive refractive-power, and which is fixed during magnification change, a second lens-group having negative refractive-power, a third lens-group having negative refractive-power, a fourth lens-group having negative refractive-power, an aperture stop, which is fixed during magnification change, and a fifth lens-group having positive refractive-power, and which is fixed during magnification change, in this order from an object-side along an optical-axis.

Abstract: A zoom lens includes: a first lens group having a negative refractive power; and a second lens group having a positive refractive power, provided in this order from an object side. Magnification is changed by moving the first lens group and the second lens group. The first lens group includes a first lens having a negative refractive power, a second lens having a positive refractive power, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, provided in this order from the object side. The zoom lens satisfies the following conditional formulae, when fw is the focal length of the entire system at the wide angle end, f1 is the focal length of the first lens group, and f2 is the focal length of the second lens group: 0.00<fw/f2<0.43??(1-5) 0.56<|f1/f2|<2.00??(2-4).

Abstract: A zoom lens includes: a first lens group having a negative refractive power; and a second lens group having a positive refractive power, provided in this order from an object side. Magnification is changed by moving the first lens group and the second lens group. The first lens group includes a first lens having a negative refractive power, a second lens, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, provided in this order from the object side. The zoom lens satisfies predetermined conditional formulae.

Abstract: A zoom lens includes: a first lens group having a negative refractive power; and a second lens group having a positive refractive power, provided in this order from an object side. Magnification is changed by moving the first lens group and the second lens group. The first lens group includes a first lens having a negative refractive power, a second lens, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, provided in this order from the object side. The zoom lens satisfies the following conditional formulae, when fw is the focal length of the entire system at the wide angle end, f1 is the focal length of the first lens group, and fG12 is the focal length of the second lens within the first lens group: ?0.20<f1/fG12<0.05 (1-3); and 0.36<|fw/f1|<0.63 (2-4).

Abstract: A zoom lens includes: a first lens group having a negative refractive power; and a second lens group having a positive refractive power, provided in this order from an object side. Magnification is changed by moving the first lens group and the second lens group. The first lens group includes a first lens having a negative refractive power, a second lens, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, provided in this order from the object side. The zoom lens satisfies the following conditional formulae, when f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, and fG12 is the focal length of the second lens within the first lens group: 0.00<|f1/f2|<1.04 (1-5); and ?1.00<f1/fG12<0.16 (2-3).

Abstract: In a zoom lens in which a first lens group having a negative refractive power and a second lens group having a positive refractive power are disposed in order from the object side and zooming is performed by moving the first lens group and the second lens group, the first lens group is formed of a first lens having a negative refractive power, a second lens having a positive refractive power, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, disposed in order from the object side. Then, when the focal length of the first lens group is taken as f1 and the focal length of the second lens group is taken as f2, the zoom lens is configured to satisfy a conditional expression give below: 0.00<|f1/f2|<1.04 ??(1-4).

Abstract: In a zoom lens in which a first lens group having a negative refractive power and a second lens group having a positive refractive power are disposed in order from the object side and zooming is performed by moving the first lens group and the second lens group, the first lens group is formed of a first lens having a negative refractive power, a second lens having a positive refractive power, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, disposed in order from the object side. Then, when the focal length of the entire system at the wide angle end is taken as fw and the focal length of the second lens group are taken as f2, the zoom lens is configured to satisfy a conditional expression give below: 0.00<fw/f2<0.35??(1-1).

Abstract: A zoom lens includes: a first lens group having a negative refractive power; and a second lens group having a positive refractive power, provided in this order from an object side. Magnification is changed by moving the first lens group and the second lens group. The first lens group includes a first lens having a negative refractive power, a second lens having a positive refractive power, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, provided in this order from the object side. The zoom lens satisfies the following conditional formulae, when fw is the focal length of the entire system at the wide angle end, and f1 is the focal length of the first lens group (G1): 0.00<|fw/f1|<0.414 (1-1).

Abstract: A zoom lens substantially consists of: a first lens group having a negative refractive power and a second lens group having a positive refractive power arranged in order from the object side; that changes magnification by moving the first lens group and the second lens group; and wherein the first lens group is configured by a first lens having a negative refractive power, a second lens, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, arranged in order from the object side. The zoom lens satisfies a predetermined conditional expression.

Abstract: A zoom lens includes: a first lens group having a negative refractive power; and a second lens group having a positive refractive power, provided in this order from an object side. Magnification is changed by moving the first lens group and the second lens group. The first lens group includes a first lens having a negative refractive power, a second lens, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, provided in this order from the object side. The zoom lens satisfies predetermined conditional formulae.

Abstract: A zoom lens includes: a first lens group having a negative refractive power; and a second lens group having a positive refractive power, provided in this order from an object side. Magnification is changed by moving the first lens group and the second lens group. The first lens group includes a first lens having a negative refractive power, a second lens, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, provided in this order from the object side. The zoom lens satisfies predetermined conditional formulae.

Abstract: A zoom lens substantially consists of a first lens group having a negative refractive power and a second lens group having a positive refractive power arranged in order from the object side; that changes magnification by moving the first lens group and the second lens group; and wherein the first lens group is configured by a first lens having a negative refractive power, a second lens, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, arranged in order from the object side. The zoom lens satisfies a predetermined conditional expression.

Abstract: A zoom lens includes: a first lens group having a negative refractive power; and a second lens group having a positive refractive power, provided in this order from an object side. Magnification is changed by moving the first lens group and the second lens group. The first lens group includes a first lens having a negative refractive power, a second lens, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, provided in this order from the object side. The zoom lens satisfies predetermined conditional formulae.

Abstract: In a zoom lens in which a first lens group having a negative refractive power and a second lens group having a positive refractive power are disposed in order from the object side and zooming is performed by moving the first lens group and the second lens group, the first lens group is formed of four lenses and the object side surface of the second lens in the first lens group is made concave on the object side in the paraxial region. When the paraxial radii of curvature of the object side surface and the image side surface of the second lens are taken as rG12F and rG12R respectively, the zoom lens satisfies a conditional expression given below: 2.0<(rG12F+rG12R)/(rG12F?rG12R)<30.0??(1-1).

Abstract: A variable-magnification optical-system substantially consists of a first-lens-group having positive-refractive-power, a second-lens-group having negative-refractive-power, a third-lens-group having negative-refractive-power, a fourth-lens-group having negative-refractive-power, an aperture-stop, and a fifth-lens-group having positive-refractive-power in this order from an object-side along an optical-axis. The second-lens-group, third-lens-group and fourth-lens-group move when magnification is changed from a wide-angle-end to a telephoto-end.

Abstract: In a zoom lens in which a first lens group having a negative refractive power and a second lens group having a positive refractive power are disposed in order from the object side and zooming is performed by moving the first and the second lens groups, the first lens group is formed of a first lens having a negative refractive power, a second lens, a third lens having a negative refractive power, and a fourth lens having a positive refractive power. Then, when the focal length of the second lens, the focal length of the entire system at the wide angle end, the focal length of the first lens group, and the focal length of the second lens group are taken as fG12, fw, f1, and f2 respectively, the zoom lens is configured to satisfy conditional expressions give below: 0.00<fw/f2<0.50??(1-1); and ?0.19<f1/fG12<0.16??(2-1).

Abstract: A zoom lens includes: a first lens group having a negative refractive power; and a second lens group having a positive refractive power, provided in this order from an object side. Magnification is changed by moving the first lens group and the second lens group. The first lens group includes a first lens having a negative refractive power, a second lens, a third lens having a negative refractive power, and a fourth lens having a positive refractive power, provided in this order from the object side. The zoom lens satisfies predetermined conditional formulae.

Abstract: A real-image variable-magnification viewfinder substantially consists of, in order from the object side: an objective lens system substantially consisting of a positive first lens, a negative second lens, a positive third lens, and a positive fourth lens; an erect optical system formed by a plurality of optical members; and a positive eyepiece lens system. The first lens and the third lens are fixed relative to the optical axis direction during magnification change, and the second lens and the fourth lens are moved in the optical axis direction during magnification change. All optical surfaces of all the optical members forming the erect optical system are planar surfaces. At least one of the optical members forming the erect optical system is made of a glass material. A predetermined conditional expression is satisfied.

Abstract: A zoom lens includes a first lens-group having positive refractive power, a second lens-group having negative refractive power, a third lens-group having positive refractive power, and a fourth lens-group having positive refractive power, in this order from an object side, and a stop located between a most image-side surface of the second lens-group and a most image-side surface of the third lens-group. Distances between the lens-groups change when magnification is changed from a wide-angle end to a telephoto end. The second lens-group consists of a negative lens, a biconcave lens and a positive lens in this order from the object side. The third lens-group consists of a positive lens, a cemented lens of a positive lens and a negative lens, a negative meniscus lens with its concave surface facing the object side, and a biconvex lens in this order from the object side. A predetermined conditional formula is satisfied.