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).

An optical system includes, in order from an object side to an image side, a first lens unit having a positive refractive power, a first focus lens unit having a negative refractive power, and a second focus lens unit having a positive refractive power. The first lens unit is fixed during focusing. The first focus lens unit and the second focus lens unit move so that a distance between the first focus lens unit and the second focus lens unit changes during focusing. The first lens unit includes a single lens which is disposed closest to an object and has a negative refractive power. A predetermined condition is satisfied.

A variable magnification optical system consists of, in order from an object side to an image side, a first lens group, a second lens group, and a subsequent lens group. The variable magnification optical system satisfies a predetermined conditional expression for a partial dispersion ratio related to F line, C line, and a wavelength of 1970.09 nm, a d-line back focus of the variable magnification optical system at a telephoto end, a back focus in any one wavelength from a wavelength of 1300 nm to a wavelength of 2325.42 nm at the telephoto end, and a d-line focal length of the variable magnification optical system at the telephoto end.

A variable magnification optical system comprises, in order from an object side, 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 and a fourth lens group G4 having negative refractive power; upon varying a magnification, a distance between the first lens group G1 and the second lens group G2 being varied, a distance between the second lens group G2 and the third lens group G3 being varied, and a distance between the third lens group G3 and the fourth lens group G4 being varied; upon focusing, the fourth lens group G4 being moved; and a predetermined conditional expression being satisfied. With such a configuration, there is provided a variable magnification optical system whose focusing lens group is compact in size and reduced in weight, so high speed and quiet focusing can be effected without lens barrel being made large in size, and further by which variations in aberrations upon varying magnification from the wide angle end state to the telephoto end state as well as variations in aberrations upon focusing from the infinite distance object to the close distance object can be superbly suppressed.

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 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.

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, 3.70<f1/(f2)<5.00, 3.20<f1/f3<5.00, where 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 zoom optical system comprises, in order from an object: a front lens group (GFS) having a positive refractive power; an M1 lens group (GM1) having a negative refractive power; an M2 lens group (GM2) having a positive refractive power; and an RN lens group (GRN) having a negative refractive power, wherein upon zooming, distances between the front lens group and the M1 lens group, between the M1 lens group and the M2 lens group, and between the M2 lens group and the RN lens group change, upon focusing from an infinite distant object to a short distant object, the RN lens group moves, the RN lens group comprises at least one lens having a positive refractive power, and at least one lens having a negative refractive power, and following conditional expressions are satisfied, 2.70<fFP/(fFN)<4.50, 0.25<(fF)/f1<0.45, where fFP: a focal length of a lens having a strongest positive refractive power in the RN lens group, fFN: a focal length of a lens having a strongest negative refractive power in the RN lens group, fF: a focal length of the RN lens group, and f1: a focal length of the front lens group.

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 the second lens group (G2) comprises a partial group that satisfies following conditional expressions, 1.40<fvr/f2<2.30, 1.80<f1/fw<3.50 where fvr: a focal length of the partial group, f2: a focal length of the second lens group (G2), f1: a focal length of the first lens group (G1), and fw: a focal length of the zoom optical system (ZL) in a wide-angle end state.

A zoom optical system comprises, in order from an object: a front lens group (GFS) having a positive refractive power; an M1 lens group (GM1) having a negative refractive power; an M2 lens group (GM2) having a positive refractive power; and an RN lens group (GRN) having a negative refractive power, wherein upon zooming, distances between the front lens group and the M1 lens group, between the M1 lens group and the M2 lens group, and between the M2 lens group and the RN lens group change, upon focusing from an infinite distant object to a short distant object, the RN lens group moves, and the M2 lens group comprises an A lens group that satisfies a following conditional expression, 1.10<fvr/fTM2<2.00, where, fvr: a focal length of the A lens group, and fTM2: a focal length of the M2 lens group in a telephoto end state.