A zoom image pickup apparatus includes a mount portion, a zoom lens which forms an image of light incident from the mount portion, and an image pickup element which is disposed at an image forming position. The zoom lens includes a plurality of lens unit, and a focusing lens unit, and the following conditional expressions (1) and (2) are satisfied:

1.5<f.sub.Lt/f.sub.Lw   (1), and

|(y.sub.w7d′−y.sub.w7d)/y.sub.w7d×100<0.66   (2).

A zoom lens is constituted by, in order from the object side: a negative first lens group; an aperture stop; a positive second lens group; a negative third lens group; and a positive fourth lens group. All of the lens groups move along the optical axis when changing magnification from the wide angle end to the telephoto end such that the distance between the first lens group and the second lens group decreases and the distance between the second lens group and the third lens group increases. The first lens group is constituted by, in order from the object side, a 1-1 lens having a negative refractive power, a 1-2 lens having a negative refractive power, and a 1-3 lens having a positive refractive power. Conditional Formula (1) below is satisfied.
1.75<ndave<1.92  (1)

A zoom lens includes a first lens group having negative refractive power; a second lens group having positive refractive power; a third lens group having negative refractive power and a fourth lens group having positive refractive power. Upon varying magnification, distances between the first lens group and the second lens group, between the second lens group and the third lens group and between the third lens group and the fourth lens group vary. The second lens group includes a front lens group, an aperture stop, and a rear lens group. Each of the front lens group and the rear lens group includes at least one positive lens. At least a part of the lenses in the second lens group is moved as a group to have a component in a direction perpendicular to an optical axis.

An image capturing lens system includes four lens groups which include eight lens elements. The four lens groups are, in order from an object side to an image side: first, second, third and fourth lens groups. The eight lens elements are, in order from the object side to the image side: first, second, third, fourth, fifth, sixth, seventh and eighth lens elements. The first and second lens elements respectively have positive and negative refractive power. At least one lens element in the second through fourth lens groups has an inflection point. A focal length of the image capturing lens system is varied by changing axial distances between the four lens groups in a zooming process. The second lens group is moved relative to the first lens group along an optical axis in the zooming process. The image capturing lens system has a long-focal-length end and a short-focal-length end.

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 variable focal length lens system includes: first to fourth lens groups alternately having negative and positive refractive power; and an aperture stop; the first to fourth lens group being arranged to allow a space between the first and second lens groups to be decreased and spaces between the second and third lens groups and between the third and fourth lens groups to be varied, the third lens group travelling to allow image-plane position variation caused by subject position variation to be compensated and satisfying a following conditional expression,
0.05<Da/R3a<0.5  (1) where Da is a distance from the aperture stop to a most image-sided lens surface in the third lens group in the wide end state, and R3a is a curvature radius of the most-image sided lens surface in the third lens group.

An inner focus lens system comprises, in order from an object side to an image side, a first lens unit, an aperture stop, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, and a fourth lens unit having a positive refractive power, wherein the first lens unit has at least one negative lens and at least one positive lens, the second lens unit has at least one negative lens and at least one positive lens, the third lens unit has at least one negative lens, the fourth lens unit has at least one positive lens, at the time of focusing on an object at a short distance from an object at infinity, the third lens unit moves to an image side so as to lengthen a distance to the second lens unit and to shorten a distance to the fourth lens unit, and the following conditional expression (1) is satisfied:
−6<f.sub.3/f<−1  (1).

The present disclosure discloses a zoom lens assembly. The zoom lens assembly comprises, sequentially along an optical axis from an object side to an image side, a first lens group comprising a first lens and a second lens; a second lens group having a positive refractive power and comprising a third lens, a fourth lens and a fifth lens; a third lens group having a negative refractive power and comprising a sixth lens; and a fourth lens group having a positive refractive power and comprising a seventh lens and an eighth lens. At least one of the first lens to the eighth lens is an aspheric lens. By changing positions of at least two lens groups in the second lens group, the third lens group and the fourth lens group on the optical axis, the zoom lens assembly switches between a wide-angle state and a telephoto state, and a focal length of the zoom lens assembly changes linearly when the zoom lens assembly switches from the wide-angle state to the telephoto state.

The zoom lens consists of, in order from an object side to an image side, a first lens group having a negative refractive power, a middle group, and a final group. During zooming, a spacing between the first lens group and the middle group changes, and a spacing between the middle group and the final group changes. During focusing, at least a part of the middle group moves, and the first lens group and the final group remain stationary with respect to an image plane. The zoom lens satisfies predetermined conditional expressions about a back focal length, a focal length, and a maximum half angle of view.

A variable magnification optical system comprising, in order from an object side, a first lens group having negative refractive power, a first intermediate lens group having positive refractive power, a second intermediate lens group having negative refractive power and a rear lens group; upon varying a magnification from a wide angle end state to a telephoto end state, a distance between the first lens group and the first intermediate lens group being varied, a distance between the first intermediate lens group and the second intermediate lens group being varied, and a distance between the second intermediate lens group and the rear lens group being varied; the rear lens group comprising at least one focusing lens group which is moved upon carrying out focusing from an infinitely distant object to a closely distant object; and predetermined conditional expressions being satisfied, thereby the focusing lens group(s) being reduced in weight.