A lens apparatus includes an operation member that is rotatable by a user operation, a zoom lens configured to perform zooming in accordance with a rotation of the operating member, and a detector configured to divide an entire zoom range from a wide-angle end to a telephoto end, and detect a zoom position of the zoom lens. A predetermined condition is satisfied.

A lens apparatus includes an operation member that is rotatable by a user operation, a zoom lens configured to perform zooming in accordance with a rotation of the operating member, and a detector configured to divide an entire zoom range from a wide-angle end to a telephoto end, and detect a zoom position of the zoom lens. A predetermined condition is satisfied.

A zoom lens includes a negative first lens group, a positive second lens group, and a subsequent lens group in order from an object side. A focusing lens group closer to an image side than the first lens group moves during focusing. The first lens group consists of a first-a lens group and a first-b lens group in order from the object side. Assuming that an average of refractive indices of the negative lenses of the first-a lens group is Nd1ave, a focal length of the focusing lens group is ff, and a focal length of the first lens group is f1, Conditional Expression (1) of 1.73<Nd1ave<1.95 and Conditional Expression (2) of 1<|ff/f1|<3 are satisfied.

A mid-wave infrared (MWIR) discrete zoom lens for use with remote surveillance and identification having a dual focal length of 9 and 6.39 inches and F #2.8 and F #2, respectively. In one case, a full field of view is about 30.8 degrees for a 9 inch focal length configuration and about 43 degrees for a 6.39 inch focal length configuration. The lens is corrected for monochromatic and chromatic aberrations over the wavelength range 5100 nm-3300 nm. The focal plane may constitute a pixel array consisting of MWIR sensitive material (e.g. InSb, HgCdTe, nBn, SLS, etc.) for use in high-resolution, wide-area imaging applications.

A lens apparatus includes an operation member that is rotatable by a user operation, a zoom lens configured to perform zooming in accordance with a rotation of the operating member, and a detector configured to divide an entire zoom range from a wide-angle end to a telephoto end, and detect a zoom position of the zoom lens. A predetermined condition is satisfied.

A lens apparatus includes an operation member that is rotatable by a user operation, a zoom lens configured to perform zooming in accordance with a rotation of the operating member, and a detector configured to divide an entire zoom range from a wide-angle end to a telephoto end, and detect a zoom position of the zoom lens. A predetermined condition is satisfied.

A zoom lens includes a negative first lens group, a positive second lens group, and a subsequent lens group in order from an object side. A focusing lens group closer to an image side than the first lens group moves during focusing. The first lens group consists of a first-a lens group and a first-b lens group in order from the object side. Assuming that an average of refractive indices of the negative lenses of the first-a lens group is Nd1ave, a focal length of the focusing lens group is ff, and a focal length of the first lens group is f1, Conditional Expression (1) of 1.73<Nd1ave<1.95 and Conditional Expression (2) of 1<|ff/f1|<3 are satisfied.

A zoom lens includes a negative first lens group, a positive second lens group, and a subsequent lens group in order from an object side. A focusing lens group closer to an image side than the first lens group moves during focusing. The first lens group consists of a first-a lens group and a first-b lens group in order from the object side. Assuming that an average of refractive indices of the negative lenses of the first-a lens group is Nd1ave, a focal length of the focusing lens group is ff, and a focal length of the first lens group is f1, Conditional Expression (1) of 1.73<Nd1ave<1.95 and Conditional Expression (2) of 1<|ff/f1|<3 are satisfied.

The zoom lens consists of, in order from an object side, a first lens group having a positive power, a second lens group having a negative power, a third lens group having a positive power, a fourth lens group having a negative power, and a fifth lens group having a positive power. An aperture diaphragm is disposed between a surface of the second lens group closest to an image side and a surface of the fourth lens group closest to the object side. The first lens group and the fifth lens group each consist of two or less lenses. A negative meniscus lens, which is convex toward the object side, is disposed to be closest to the object side of the second lens group. A negative meniscus lens, which is convex toward the image side, is disposed to be closest to the image side of the fourth lens group.

A zoom lens consists of a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power in this order from an object side. The third lens group includes a cemented lens closest to the object side and a cemented lens closest to an image side, and the fourth lens group consists of a negative lens and a positive lens in this order from the object side. Distances between the lens groups change, and the fifth lens group is fixed, and at least the first lens group and the fourth lens group move when magnification is changed from the wide angle end to the telephoto end.