Abstract: A zoom lens system includes, in order from an object, a first lens group having positive power, a second lens group having negative power, a third lens group having positive power, a fourth lens group having positive power, and a fifth lens group having positive power. Upon zooming from a wide-angle end state to a telephoto end state, the first and fifth lens groups moves with respect to the image plane, the second lens group moves at first to the image and then to the object, and the third and fourth lens groups move to the object such that a distance between the first and second lens groups increases, a distance between the second and third lens group decreases, a distance between the third and fourth lens groups decreases, and a distance between the fourth and fifth lens groups increases. Given conditional expressions are satisfied.

Abstract: A zoom lens system includes, in order from an object, a first lens group having positive power, a second lens group having negative power, a third lens group having positive power, a fourth lens group having positive power, and a fifth lens group having positive power. Upon zooming from a wide-angle end state to a telephoto end state, the first and fifth lens groups moves with respect to the image plane, the second lens group moves at first to the image and then to the object, and the third and fourth lens groups move to the object such that a distance between the first and second lens groups increases, a distance between the second and third lens group decreases, a distance between the third and fourth lens groups decreases, and a distance between the fourth and fifth lens groups increases. Given conditional expressions are satisfied.

Abstract: The common zoom optical system is provided that is almost commonly used in a plurality of zoom lenses as a component and that is capable of suppressing fluctuation in aberrations and deviation in the position of the image plane, wherein the common zoom optical system is almost commonly used in a plurality of zoom lenses as a component, and when zooming from a wide-angle end state of a plurality of the zoom lenses composed by use of the common zoom optical system to a telephoto end state thereof, a moving path of the common zoom optical system differs for each zoom lens.

Abstract: A zoom lens system includes, in order from an object, a first lens group having positive power, a second lens group having negative power, a third lens group having positive power, a fourth lens group having positive power, and a fifth lens group having positive power. Upon zooming from a wide-angle end state to a telephoto end state, the first and fifth lens groups moves with respect to the image plane, the second lens group moves at first to the image and then to the object, and the third and fourth lens groups move to the object such that a distance between the first and second lens groups increases, a distance between the second and third lens group decreases, a distance between the third and fourth lens groups decreases, and a distance between the fourth and fifth lens groups increases. Given conditional expressions are satisfied.

Abstract: A variable focal length lens system comprises, from the object side, a positive first lens group, a positive second lens group and a negative third lens group. The lens groups are moved toward the object side such that, when changing from wide angle to telephoto, distance between the first lens group and the second lens group is increased and distance between the second lens group and the third lens group is decreased. An aperture stop disposed in the vicinity of the second lens group moves together with the second lens group; the third lens group is composed of a positive lens with the convex surface facing the image side and a negative lens disposed away from the positive lens toward the image side and having the concave surface facing the object side; and the positive lens is a double aspherical lens and satisfies predetermined conditions.

Abstract: A variable focal length lens system comprising a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power and a third lens group G3 having a negative refractive power from the side of an object in this order; the respective lens groups are moved toward the object side in such a manner that, when the lens positional state is changed from a wide angle end state to a telephoto end state, a distance between the first lens group G1 and the second lens group G2 is increased and a distance between the second lens group G2 and the third lens group G3 is decreased; an aperture stop S is disposed in the vicinity of the second lens group G2; the aperture stop is moved together with the second lens group G2 in response to a change in the lens positional state so that the third lens group G3 is composed of a positive lens with the convex surface facing the side of an image and a negative lens which is disposed away from the positive lens with an air distance therebe