Abstract: A zoom lens system includes a negative first lens group, a positive second and third lens groups, wherein distances between the lens groups change during zooming from the short to long focal length extremities. The following conditions (1) and (2) are satisfied: 0.20<F2/Ft<0.45??(1), and ?3.00<F2/fm<?1.00??(2), wherein F2 designates the combined focal length of the second lens group, Ft designates the focal length of the entire the zoom lens system at the long focal length extremity, fm designates the focal length of the surface on the image side of the lens element closest to the image side within the second lens group, fm=(1?nm)/rm, and nm and rm respectively designate the refractive index at the d-line, and the radius of curvature of the surface on the image side of, the lens element provided closest to the image side within the second lens group.

Abstract: A zoom lens system includes a negative first lens group, a positive second and third lens groups, wherein distances between the lens groups change during zooming from the short to long focal length extremities. The following conditions (1) and (2) are satisfied: 0.20<F2/Ft<0.45??(1), and ?3.00<F2/fm<?1.00??(2), wherein F2 designates the combined focal length of the second lens group, Ft designates the focal length of the entire the zoom lens system at the long focal length extremity, fm designates the focal length of the surface on the image side of the lens element closest to the image side within the second lens group, fm=(1?nm)/rm, and nm and rm respectively designate the refractive index at the d-line, and the radius of curvature of the surface on the image side of, the lens element provided closest to the image side within the second lens group.

Abstract: A zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, in this order from the object; upon zooming from the short focal length extremity to the long focal length extremity, the first to the fourth lens groups move along the optical axis of the zoom lens system in a manner so that the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the distance between the third lens group and the fourth lens group increases; wherein the zoom lens system satisfies the following condition: 13.50<f1/fw<19.50??(1) wherein f1 designates the focal length of the positive first lens group; and fw designates the focal length of the entire zoom lens system at the short focal length extremity.

Abstract: A wide-angle lens system includes a negative first lens group, a negative second lens group and a positive third lens group, in this order from the object. The first lens group includes a negative meniscus lens element having the convex surface facing toward the object, and a positive lens element having a convex surface facing toward the object, in this order from the object. The first lens group includes at least one aspherical surface. The second lens group includes a negative meniscus lens element having the convex surface facing toward the object, and cemented lens elements having a positive lens element and a negative lens element, in this order from the object. The third lens group includes cemented lens elements having a negative lens element and a positive lens element, and a positive lens element having a convex surface facing toward the image, in this order from the object.

Abstract: A zoom lens system includes a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, in this order from the object; upon zooming from the short focal length extremity to the long focal length extremity, the first to the fourth lens groups move along the optical axis of the zoom lens system in a manner so that the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the distance between the third lens group and the fourth lens group increases; wherein the zoom lens system satisfies the following condition: 13.50<f1/fw<19.50 ??(1) wherein f1 designates the focal length of the positive first lens group; and fw designates the focal length of the entire zoom lens system at the short focal length extremity.

Abstract: A wide-angle lens system includes a negative first lens group, a negative second lens group and a positive third lens group, in this order from the object. The first lens group includes a negative meniscus lens element having the convex surface facing toward the object, and a positive lens element having a convex surface facing toward the object, in this order from the object. The first lens group includes at least one aspherical surface. The second lens group includes a negative meniscus lens element having the convex surface facing toward the object, and cemented lens elements having a positive lens element and a negative lens element, in this order from the object. The third lens group includes cemented lens elements having a negative lens element and a positive lens element, and a positive lens element having a convex surface facing toward the image, in this order from the object. The wide-angle lens system satisfies the following conditions: 1.30<f3/f<1.70??(1) ?13.50<f2/f<?3.