Abstract: A lens system includes sequentially from an object side: a first lens group having a positive refractive power; an aperture diaphragm; a second lens group having a positive refractive power; and a third lens group having a positive refractive power and moving along a direction of an optical axis when focusing from an object at infinity to a close object. Assuming that L is a distance from a lens surface of the first lens group closest to the object side to a lens surface closest to an image side on the optical axis, Y is a maximum image height, f1 is a focal length of the first lens group, and f is a focal length of the entire lens system, the lens system satisfies the following conditions: 1.0<L/Y<2.3, and 1<f1/f<3.

Abstract: The rear attachment lens has a positive refractive power as a whole, and is attached to an image side of a main lens so as to change a focal length of the whole lens system after attachment to a focal length longer than a focal length of the main lens. The rear attachment lens includes a most object side lens that is a lens which has a negative refractive power and is disposed to be closest to an object side, and a most image side lens that is a lens which has a positive refractive power and is disposed to be closest to the image side.

Abstract: The rear attachment lens has a positive refractive power as a whole, and is attached to an image side of a main lens so as to change a focal length of the whole lens system after attachment to a focal length longer than a focal length of the main lens. The rear attachment lens includes a most object side lens that is a lens which has a negative refractive power and is disposed to be closest to an object side, and a most image side lens that is a lens which has a positive refractive power and is disposed to be closest to the image side.

Abstract: A zoom lens is constituted by, in order from the object side to the image side: a positive first group which is fixed when changing magnification, a negative second lens group which moves when changing magnification, a negative third lens group which moves when changing magnification, and a positive fourth lens group which is fixed when changing magnification. The first lens group is constituted by a 1a lens of a negative meniscus shape, a positive 1b lens, and a positive 1c lens. The second lens group is constituted by a negative 2a lens, a biconcave 2b lens, a positive 2c lens, and a negative 2d lens. The third lens group is constituted by a negative 3a lens and a positive 3b lens. The fourth lens group includes a 4a lens, an aperture stop, and a positive 4b lens, which are consecutively provided from the most object side thereof.

Abstract: A zoom lens is constituted by, in order from the object side to the image side: a positive first group which is fixed when changing magnification, a negative second lens group which moves when changing magnification, a negative third lens group which moves when changing magnification, and a positive fourth lens group which is fixed when changing magnification. The first lens group is constituted by a 1a lens of a negative meniscus shape, a positive 1b lens, and a positive 1c lens. The second lens group is constituted by a negative 2a lens, a biconcave 2b lens, a positive 2c lens, and a negative 2d lens. The third lens group is constituted by a negative 3a lens and a positive 3b lens. The fourth lens group includes a 4a lens, an aperture stop, and a positive 4b lens, which are consecutively provided from the most object side thereof.