A variable magnification optical system comprising, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a rear lens group having negative refractive power; upon varying a magnification from a wide angle end state to a tele photo end state, a distance between the first lens group and the second lens group being varied, a distance between the second lens group and the third lens group being varied, and a distance between the third lens group and the rear lens group being varied; the third lens group or the rear lens group comprising a focusing lens group which is moved upon carrying out focusing from an infinitely distant object to a closely distant object; and predetermined conditional expression(s) being satisfied, thereby various aberrations being corrected superbly.

A zoom lens system includes: a first group of lenses having positive power; a second group of lenses having negative power; a third group of lenses having positive power; a fourth group of lenses having negative power; and a fifth group of lenses having power, which are arranged in this order from an object toward an image. While this system is zooming, intervals between these groups change and the fifth group of lenses moves toward the object. This system satisfies 0.12<T35t/TLt<0.25, where T35t is a distance, measured at telephoto end, from one surface, closest to the image, of the third group of lenses to another surface, closest to the object, of the fifth group of lenses, and TLt is a distance, measured at the telephoto end, from one surface, closest to the object, of the first group of lenses to an image plane.

An optical system includes a front lens group and a rear lens group that are disposed in order from an object side to an image side of the optical system, the front lens group having a positive refractive power and the rear lens group having a negative refractive power. The rear lens group consists of a lens unit Ln1 that is arranged to move towards the image side when focusing and that has a negative refractive power, and a lens unit Ln2 that is disposed closer to the image side than the lens unit Ln1 and that has a negative refractive power. The front lens group includes a lens unit Lpf arranged to move during focusing. The rear lens group satisfies a predetermined conditional expression.

A zoom lens includes an N-1-th lens unit disposed second closest to the image side and an N-th lens unit disposed closest to the image side. The N-1-th lens unit and the N-th lens unit each includes a cemented lens, and move at zooming. For at least one of the N-1-th lens unit and the N-th lens unit, the relationship between the radius of curvature of a cemented surface of the cemented lens and the distance from the cemented surface to an image plane, the value of the larger amount of the amount of movement of the N-1-th lens unit and the amount of movement of the N-th lens unit at zooming from the wide-angle end to the telephoto end, the overall lens length at the wide-angle end, the focal length of the zoom lens at the wide-angle end, and a back focus at the wide-angle end are determined.

A zoom lens ZL includes: a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, and a third lens unit L3 having a positive refractive power, an N1th lens unit, and an Nth lens unit, the lens units being arranged in order from an object side to an image side. The N1th lens unit and the Nth lens unit are located on the image side with respect to an aperture stop SP.

In an optical system according to each exemplary embodiment, an interval between adjacent lens units changes in focusing from an infinite-distance object to a close-distance object, and a first in-focus state in which =1.2 is obtained can be caused, where is a lateral magnification of an entire system. The optical system according to each exemplary embodiment includes a plurality of focus lens units, and out of a focus lens unit having a largest absolute value of a focus sensitivity and a focus lens unit having a second largest absolute value of a focus sensitivity in a state in which focus is put on an infinite-distance object, a focus lens unit disposed on an object side is a lens unit LA, and a focus lens unit disposed on an image side is a lens unit LB. A partial optical system LC including all lenses disposed on the image side of the lens unit LB has negative refractive power. The partial optical system LC satisfies a predetermined conditional expression.

A zoom optical system ZL comprises, in order from an object: a first lens group (G1) having a positive refractive power; a second lens group (G2) having a negative refractive power; a third lens group (G3) having a positive refractive power; and a subsequent lens group (GR), wherein upon zooming, a distance between the first lens group (G1) and the second lens group (G2) changes, a distance between the second lens group (G2) and the third lens group (G3) changes, and a distance between the third lens group (G3) and the subsequent lens group (GR) changes, the subsequent lens group (GR) comprises a focusing lens group that moves upon focusing, and following conditional expressions are satisfied, 0.18<(fF)/f1<0.30, 0.84<(f2)/f3<1.20, where fF: a focal length of the focusing lens group, f1: a focal length of the first lens group (G1), f2: a focal length of the second lens group (G2), and f3: a focal length of the third lens group (G3).

A variable magnification optical system comprising, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a rear lens group having negative refractive power; upon varying a magnification from a wide angle end state to a tele photo end state, a distance between the first lens group and the second lens group being varied, a distance between the second lens group and the third lens group being varied, and a distance between the third lens group and the rear lens group being varied; the third lens group or the rear lens group comprising a focusing lens group which is moved upon carrying out focusing from an infinitely distant object to a closely distant object; and predetermined conditional expression(s) being satisfied, thereby various aberrations being corrected superbly.

A first lens group (G1) having positive refractive power, a second lens group (G2) having negative refractive power, a third lens group (G3) having positive refractive power, a fourth lens group (G4) having negative refractive power, and a fifth lens group (G5) having positive refractive power are arranged in order from an object, and zooming is performed by changing distances between each lens group, and the first lens group (G1) is composed of three or more lenses, the fourth lens group (G4) is composed of two or less lenses, and the fifth lens group (G5) is composed of two or less lenses and moves to an image surface side upon zooming from a wide angle end state to a telephoto end state, and the following conditional expression (1) is satisfied.
8.40<f1/(f2)(1) where, f1 denotes a focal length of the first lens group (G1), and f2 denotes a focal length of the second lens group (G2).

A zoom optical system (ZL) comprises: a first lens group (G1) disposed closest to an object and having a positive refractive power; an aperture stop (S) disposed closer to an image than the first lens group (G1); a positive lens component disposed so as to oppose the image side of the aperture stop (S); and a lens group (G3) having the positive lens component, wherein a distance between the first lens group (G1) and the lens group (G3) having the positive lens component changes during zooming, at least one lens surface of the positive lens component has an aspherical surface, and the following conditional expression,

0.40<fp/fGp<3.60

is satisfied,
where fp: a focal length of the positive lens component, and fGp: a focal length of the lens group (G3) having the positive lens component.