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 in order from 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 lens unit having a negative refractive power. The second lens unit is a focusing lens unit. At the time of zooming from a wide angle end to a telephoto end, the third lens unit and the lens unit having a negative refractive power positioned on an object side of the third lens unit move, and the following conditional expression (1) is satisfied:

φ.sub.L1<φ.sub.3GL1   (1).

A zoom lens system includes a positive first lens group, a negative second lens group, a positive intermediate lens group, and a negative image-side lens group. Upon zooming from the short to long focal length extremities, a distance between the first and second lens groups increases, and a distance between the second and intermediate lens groups decreases. The image-side lens group consists of two lens elements. The following conditions are satisfied:

−6.0<f1/f2<−4.3,

−5.4<f1/fIMG<−3.9,

and

0.3<D2/fw<3.0.

f1, f2 and fIMG designate the focal lengths of the first, second and the image-side lens groups, respectively. D2 designates a distance between the second lens group and the intermediate lens group, at the short focal length extremity. fw designates the focal length of the zoom lens system at the short focal length extremity.

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.

The zoom lens includes, in order from an object side, a positive first lens group G1, a negative second lens group G2, a positive third lens group G3, a diaphragm, and a fourth lens group G4. During zooming, only the second lens group G2 and the third lens group G3 move. The first lens group G1 includes, in order from the object side, a cemented lens that is formed by cementing a positive lens and a negative meniscus lens convex toward the object side, a positive lens, and a negative lens. A conditional expression (1): −0.8<f1a/f1b<0 is satisfied, where f1a is a composite focal length of the first to third lenses from the object side of the first lens group G1, and f1b is a focal length of the fourth lens.

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 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.

An optical lens, in order from an object side to an image-forming side, includes: a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive refractive power, a fourth lens having positive refractive power, a fifth lens having negative refractive power, a sixth lens having negative refractive power, a seventh lens having negative refractive power and an eighth lens having refractive power.

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.

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.