This optical system (LS) has an aperture diaphragm (S) and a negative lens (L4) disposed closer to an object side than the aperture diaphragm (S) and satisfies the following conditional expression.

−0.010<ndN1−(2.015−0.0068×νdN1),

50.00<νdN1<65.00, 0.545<θgFN1,

−0.010<θgFN1−(0.6418−0.00168×νdN1).

Where, ndN1 is a refractive index of the negative lens with respect to a d-line, vdN1 is an Abbe number of the negative lens based on the d-line, and θgFN1 is a partial dispersion ratio of the negative lens.

A zoom lens includes a positive first lens group, a negative second lens group, a positive third lens group, a positive fourth lens group, and a fifth lens group in order from an object side. In a case of zooming, an interval with an adjacent lens group is changed. The third lens group includes two positive lenses consecutively arranged in order from a side closest to the object side to an image side. The fifth lens group consists of a negative meniscus lens having a concave surface toward the object side and a positive lens having a convex surface toward the object side in order from the object side to the image side.

Provided is a zoom lens including, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a negative refractive power. In the zoom lens, an interval between each pair of adjacent lens units is changed during zooming, and the first lens unit is configured not to move for zooming. Further, a total length DT of the zoom lens at a telephoto end, a focal length fT of the zoom lens at the telephoto end, a distance BW of a back focus at a wide-angle end, a total length DW of the zoom lens at the wide-angle end, and a focal length f3 of the third lens unit are each appropriately set.

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 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.

Provided are a zoom lens 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, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power, in which distances between the respective lens groups are changed to change magnification, the first lens group consists of one single lens having spherical surfaces on both sides, the single lens is a positive meniscus lens having a convex shape toward the object side, at a time of magnification change from a wide-angle end to a telephoto end, the second lens group moves along a path convex toward the image side, and a predetermined conditional expression is satisfied, and an imaging apparatus including the zoom lens.

A variable power optical system (ZL) used for an optical apparatus, such as a camera (1), includes, in order from an object: 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 positive refractive power. The distance between the respective lens groups changes upon zooming from the wide-angle end state to the telephoto end state. The third lens group (G3) includes: an intermediate group (G3b) constituted by a positive lens, a negative lens, a negative lens, and a positive lens; and an image side group (G3c) having negative refractive power and disposed to an image side of the intermediate group (G3b). Upon focusing, the position of the intermediate group (G3b) with respect to the image plane is fixed and the image side group (G3c) moves along the optical axis.

A zoom lens includes, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a positive refractive power, and a fifth lens unit having a negative refractive power. During zooming, each distance between adjacent lens units changes. During zooming from a wide-angle end to a telephoto end, the first lens unit moves toward the object side, a distance between the third lens unit and the fourth lens unit decreases, and a distance between the fourth lens unit and the fifth lens unit decreases. The number of optical elements each having a refractive power in the first lens unit is two or less. Predetermined conditions are satisfied.

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.

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.