A zoom lens comprising in order from an object side, a first lens unit having a negative refractive power, a second lens unit having a negative refractive power, a lens unit having a positive refractive power, and a rearmost lens unit having a negative refractive power, and the rearmost lens unit is positioned nearest to an image in the plurality of lens units, and at the time of zooming, distances between the lens units in the plurality of lens units change. Moreover, an image pickup apparatus includes the zoom lens, and an image pickup element having an image pickup surface.

Provided is a small zoom lens having a high zoom ratio and easily designed to achieve favorable optical properties in an entire zooming range. A zoom lens includes, in order from object side to image side, a positive first unit, a negative second unit, an aperture stop, and a rear group including multiple units. Intervals between the adjacent units are changed during zooming. In the rear group, a positive lens unit is arranged on the most image side, and a negative lens unit is on the object side of the positive lens unit. The aperture stop not moving for zooming, but the second unit and the negative lens unit moving during zooming. Focal lengths of the second unit and the positive and negative lens units, and movement amounts of the second and negative lens units, respectively, during zooming from wide angle end to telephoto end are appropriately set.

Provided is a small zoom lens having a high zoom ratio and easily designed to achieve favorable optical properties in an entire zooming range. A zoom lens includes, in order from object side to image side, a positive first unit, a negative second unit, an aperture stop, and a rear group including multiple units. Intervals between the adjacent units are changed during zooming. In the rear group, a positive lens unit is arranged on the most image side, and a negative lens unit is on the object side of the positive lens unit. The aperture stop not moving for zooming, but the second unit and the negative lens unit moving during zooming. Focal lengths of the second unit and the positive and negative lens units, and movement amounts of the second and negative lens units, respectively, during zooming from wide angle end to telephoto end are appropriately set.

A variable magnification optical system includes: in order from an object 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 an image-side lens unit. The image-side lens unit includes a lens belonging to a first region and a lens belonging to a second region. At a time of changing magnification, the second lens unit and the third lens unit move.

A variable magnification optical system includes, sequentially from an object 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, and a fifth lens unit having a positive refractive power, and each of the lens units makes a different movement relatively to a lens unit that is adjacently positioned at least at one of a time of changing magnification, a time of focusing, and a time of image stabilization.

A variable magnification optical system includes, sequentially from an object 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, and a fifth lens unit having a positive refractive power, and each of the lens units makes a different movement relatively to a lens unit that is adjacently positioned at least at one of a time of changing magnification, a time of focusing, and a time of image stabilization.

A zoom lens system includes: a first lens group having a negative refractive power; a second lens group having a positive refractive power; and an aperture between the first and second lens groups, wherein the first lens group and the second lens group are sequentially arranged from an object side to an image side, wherein the zoom lens system performs zooming and focusing by moving the second and first lens groups, respectively, along an optical axis, and satisfies
2.5<(f.sub.w/f.sub.t)×(T.sub.w/Y)<4.5, where f.sub.w denotes an entire focal length at a wide-angle end, f.sub.t denotes an entire focal length at a telephoto end, and Tw denotes a distance between an image plane and an object side lens surface of a lens closest to the object side of the first lens group at the wide-angle end, and Y denotes a radical axis image height.

A zoom lens system includes a positive first lens group, and a rear lens group behind the first lens group, in that order from the object side. The first lens group includes at least one positive single lens element, a negative meniscus lens element having a convex surface on the object side, and at least one positive lens element, in that order from the object side. A distance between the first lens group and the rear lens group increases upon zooming from the short to long focal length extremities. The following conditions (1) and (2) are satisfied:

fG1/fn<−1.50  (1), and

65<νp.sub.ave  (2),

wherein fG1 designates the focal length of the first lens group, fn designates the focal length of the negative meniscus lens element, and νp.sub.ave designates the average value of the Abbe numbers with respect to the d-line of the positive lens elements.

A lens barrel which stably secures strength of a lens barrel without hampering miniaturization thereof. In an inner peripheral portion of a rotary cylinder rotatively driven while being inhibited from moving in a direction of an optical axis on an outer peripheral side of a straight advance cylinder which is movable in the direction of the optical axis while being inhibited from rotating on an outer peripheral side of a cam cylinder and has a through cam groove through which a first projecting portion of the cam cylinder passes, second projecting portions are provided on opposite sides of a straight advance groove of the rotary cylinder, with which the first projecting portion is to be engaged, in a circumferential direction. In an outer peripheral portion of the straight advance cylinder, circumferential grooves with which the second projecting portions are to be engaged are provided in the circumferential direction.

Provided is a zoom lens including, in order from an object side: a first lens unit not moving for zooming; a second lens unit moving during the zooming; at least one lens unit moving during the zooming; and a rear lens group. The first lens unit includes a first lens sub unit not moving for focusing, and a second lens sub unit moving during the focusing. The first lens sub unit includes a negative lens and a positive lens. A focal length of the first lens unit, a distance on an optical axis from a lens surface closest to an image side of the first lens sub unit to a rear principal point position of the first lens sub unit, and a focal length of the zoom lens at a telephoto end are appropriately set.