The imaging lens consists of, in order from the object side, a first positive lens group, a stop, a second positive lens group, and a third negative lens group. During focusing, the first lens group and the second lens group move integrally. The first lens group consists of three or less lenses. The first lens group includes a cemented lens in which a negative lens and a positive lens are cemented in order from the object side. The third lens group consists of, in order from the object side, a negative aspheric lens, a negative lens, and a positive lens. The lens closest to the image side in the second lens group is a biconvex lens, and the imaging lens satisfies a predetermined conditional expression regarding the radius of curvature of the surface of the biconvex lens.

The imaging lens consists of, in order from the object side, a first positive lens group, a stop, a second positive lens group, and a third negative lens group. During focusing, the first lens group and the second lens group move integrally. The first lens group consists of three or less lenses. The first lens group includes a cemented lens in which a negative lens and a positive lens are cemented in order from the object side. The third lens group consists of, in order from the object side, a negative aspheric lens, a negative lens, and a positive lens. The lens closest to the image side in the second lens group is a biconvex lens, and the imaging lens satisfies a predetermined conditional expression regarding the radius of curvature of the surface of the biconvex lens.

The imaging lens consists of, in order from the object side, a first positive lens group, a stop, a second positive lens group, and a third negative lens group. During focusing, the first lens group and the second lens group move integrally. The first lens group consists of three or less lenses. The first lens group includes a cemented lens in which a negative lens and a positive lens are cemented in order from the object side. The third lens group consists of, in order from the object side, a negative aspheric lens, a negative lens, and a positive lens. The lens closest to the image side in the second lens group is a biconvex lens, and the imaging lens satisfies a predetermined conditional expression regarding the radius of curvature of the surface of the biconvex lens.

A rear converter lens consists of, in order from the object side, a positive first lens group, a negative second lens group, and a positive third lens group. The first lens group consists of a cemented lens in which a negative lens concave toward the image side and a positive lens convex toward the object side are cemented, the second lens group consists of a cemented lens in which a negative lens concave toward the image side, a positive lens convex toward both sides, and a negative lens concave toward the object side are cemented, and the third lens group consists of, in order from the object side, a third lens group-first lens that is a positive lens convex toward the object side and a third lens group-second lens that is a negative lens.

A rear converter lens consists of three lens groups of, in order from its object-side, a first lens-group having positive refractive power; a second lens-group having negative refractive power; and a third lens-group having positive refractive power. The first lens-group consists of a cemented lens of a negative lens having a concave surface facing an image-side of the rear converter lens and a positive lens cemented together in order from the object-side. The second lens-group consists of a cemented lens of a negative lens, a lens having a biconvex shape, and a negative lens cemented together in order from the object-side. The third lens-group includes a lens having a convex surface facing the object-side furthest toward the object-side. When the focal length of the third lens-group is f3 and the focal length of the rear converter lens is cf, conditional expression (1) (1.9<f3/cf<0.4) is satisfied.

A rear converter lens consists of three lens groups of, in order from its object-side, a first lens-group having positive refractive power; a second lens-group having negative refractive power; and a third lens-group having positive refractive power. The first lens-group consists of a cemented lens of a negative lens having a concave surface facing an image-side of the rear converter lens and a positive lens cemented together in order from the object-side. The second lens-group consists of a cemented lens of a negative lens, a lens having a biconvex shape, and a negative lens cemented together in order from the object-side. The third lens-group includes a lens having a convex surface facing the object-side furthest toward the object-side. When the focal length of the third lens-group is f3 and the focal length of the rear converter lens is cf, conditional expression (1) (1.9<f3/cf<0.4) is satisfied.

A single focal length lens system includes a front lens unit and a rear lens unit, and does not include any other lens unit. The front lens unit includes a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a negative refractive power. Each of the first lens unit and the second lens unit includes a positive lens and a negative lens, and the first lens unit and the second lens unit do not move all the time. An aperture stop is disposed on the image side of the second lens unit. Any one of the lens units positioned on the image side of the second lens unit is a focusing lens unit, and the following conditional expression (1) is satisfied:
0.06<|f.sub.G3/f|<0.4(1)

A single focal length lens system includes a front lens unit and a rear lens unit, and does not include any other lens unit. The front lens unit includes a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a negative refractive power. Each of the first lens unit and the second lens unit includes a positive lens and a negative lens, and the first lens unit and the second lens unit do not move all the time. An aperture stop is disposed on the image side of the second lens unit. Any one of the lens units positioned on the image side of the second lens unit is a focusing lens unit, and the following conditional expression (1) is satisfied:
0.06<|f.sub.G3/f|<0.4(1)