A zoom lens includes, in order from an object side to an image side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and three or more lens units. A distance between adjacent lens units varies during zooming. A predetermined condition is satisfied.

An optical system for imaging an object onto an image plane of a microscope comprises a first lens group and a fourth lens group which are stationary, and a second lens group and a third lens group which are independently movable along an optical axis (O) of the optical system for focusing the object onto the image plane while zooming between a short focal length extremity and a long focal length extremity.

In an image pickup apparatus including an optical system and an image pickup element, the optical system includes, in order from an object side to an image side, lens(es), an aperture stop, and lens(es). The lens arranged at the most image side in the optical system is a negative lens, and an infrared cut film is formed on at least one lens surface in the optical system. An optical axial distance from the exit pupil of the optical system to the image plane when focusing on an infinite object, an optical axial distance from the lens surface provided with the infrared cut film to the image plane when focusing on the infinite distance object, the curvature radius of the lens surface provided with the infrared cut film, and a radius of a circle circumscribed about an effective imaging area of the image pickup element are appropriately set.

A zoom optical system consists of a first lens group having negative refractive power, a second lens group having positive refractive power, and a rear lens group which are disposed in order from an object. The rear lens group comprises a last lens group and an F lens group in order from a side closest to an image. Lens groups forming the first lens group, the second lens group, and the rear lens group are configured in such a manner that, upon zooming, the respective lens groups move and a distance between the lens groups adjacent to each other changes. At least a part of the F lens group is configured to move upon focusing. Further, the following conditional expression is satisfied.
0.220<f1/fE<0.280
where f1: a focal length of the first lens group, and fE: a focal length of the last lens group.

A magnification-variable optical system having a small size, a wide angle of view, and high optical performance, an optical apparatus including the magnification-variable optical system, and a method for manufacturing the magnification-variable optical system are provided, the magnification-variable optical system ZL being used for an optical apparatus and includes a first lens group G1 having a negative refractive power, and a rear group GR including at least one lens group disposed on an image side of the first lens group G1, and is configured so that a distance between lens groups adjacent to each other changes at magnification change and a condition expressed by predetermined condition expressions is satisfied.

A zoom optical system consists of a first lens group having negative refractive power, a second lens group having positive refractive power, and a rear lens group which are disposed in order from an object. The rear lens group comprises a last lens group and an F lens group in order from a side closest to an image. Lens groups forming the first lens group, the second lens group, and the rear lens group are configured in such a manner that, upon zooming, the respective lens groups move and a distance between the lens groups adjacent to each other changes. At least a part of the F lens group is configured to move upon focusing. Further, the following conditional expression is satisfied.

0.220<f1/fE<0.280 where f1: a focal length of the first lens group, and fE: a focal length of the last lens group

Composing, in order from an object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power and at least one lens group G3; upon varying magnification, a distance between the first lens group G1 and the second lens group G2, a distance between the second lens group G2 and a lens group G3 at an image side of the second lens group G2 and adjacent thereto, being varied; and a given conditional expression being satisfied; thereby providing a variable magnification optical system having a superb optical performance upon focusing, an optical device and a method for manufacturing the variable magnification optical system.

A magnification-variable optical system having a small size, a wide angle of view, and high optical performance, an optical apparatus including the magnification-variable optical system, and a method for manufacturing the magnification-variable optical system are provided, the magnification-variable optical system ZL being used for an optical apparatus and includes a first lens group G1 having a negative refractive power, and a rear group GR including at least one lens group disposed on an image side of the first lens group G1, and is configured so that a distance between lens groups adjacent to each other changes at magnification change and a condition expressed by predetermined condition expressions is satisfied.

A zoom lens includes a plurality of lens units. The plurality of lens units consist of, in order from an object side to an image side, a first lens unit having a negative refractive power, a middle group including one or more lens units, and a final lens unit having a negative refractive power. Each distance between adjacent lens units changes during zooming. The first lens unit includes at least three negative lenses. Predetermined conditions are satisfied.

A zoom lens includes a plurality of lens units. The plurality of lens units consist of, in order from an object side to an image side, a first lens unit having a negative refractive power, a middle group including one or more lens units, and a final lens unit having a negative refractive power. Each distance between adjacent lens units changes during zooming. The first lens unit includes at least three negative lenses. Predetermined conditions are satisfied.