A zoom lens includes, in order from an object along an optical axis: a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group having a negative refractive power; a fourth lens group; and a fifth lens group. When the zoom lens performs varying magnification, the distance between the first and second lens groups changes, the distance between the second and third lens groups changes, the distance between the third and fourth lens groups changes, the distance between the fourth and fifth lens groups changes, the second and fourth lens groups move along the same trajectory along the optical axis, and at least the third lens group moves along the optical axis.

An optical system (ZL(1)) comprises a plurality of lens groups including a first focusing lens group (G2) and a second focusing lens group (G4) that are disposed side by side on an optical axis, and the second focusing lens group (G4) is disposed at a position closer to an image surface than the first focusing lens group (G2). The first focusing lens group (G2) has positive refractive power, and moves toward an object along the optical axis from focusing on an infinite-distance object to focusing on a short-distance object. The second focusing lens group (G4) moves toward the image surface along the optical axis from focusing on the infinite-distance object to focusing on the short-distance object. The optical system (ZL(1)) satisfies the following conditional expression. 020<F1/F2<0.50 where F1 is the lateral magnification of the first focusing lens group at the time of focusing on the infinite-distance object, and F2 is the lateral magnification of the second focusing lens group at the time of focusing on the infinite-distance object.

A zoom lens includes, in order from an object side to an image side, a lens unit Ln having the highest negative refractive power of all the following lens units, a lens unit Lm2 having positive refractive power, a lens unit Lm having negative refractive power, and a rear lens group Lp including one or more lens units and having overall positive refractive power. During zooming, a distance between every adjacent lens units varies. During focusing from an infinite distance to a minimum object distance, the lens unit Ln and the lens unit Lm move toward the object side. The focal length F.sub.Lm of the lens unit Lm and the focal length F.sub.Lm2 of the lens unit Lm2 are appropriately set.

A zoom lens system includes: a primary image forming lens group that forms light from an object side into an intermediate image and a relay lens group that forms light from the intermediate image into a final image. The primary image forming lens group includes, in order from the object side, a first fixed lens group G1 with negative refractive power, a stop St, and a second fixed lens group G2 with positive refractive power, and the relay lens group includes, in order from the object side, a third fixed lens group G3 with negative refractive power, a first moving lens group G4 with positive refractive power, and a second moving lens group G5 with positive refractive power.

The present disclosure is directed to an optical system internally having an intermediate imaging position that is conjugated to a magnification conjugate point on a magnification side and a reduction conjugate point on a reduction side, respectively, the optical system including: a magnification optical system having A (A is an integer of three or more) pieces of lens elements, positioned on the magnification side with respect to the intermediate imaging position; and a relay optical system having B (B is an integer of two or more) pieces of lens elements, positioned on the reduction side with respect to the intermediate imaging position. A first lens group composed of pieces ( is one or more and less than B) of lens elements positioned first from the magnification side in the relay optical system has a negative power.

A zoom lens includes, in order from an object along an optical axis: a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group having a negative refractive power; a fourth lens group; and a fifth lens group. When the zoom lens performs varying magnification, the distance between the first and second lens groups changes, the distance between the second and third lens groups changes, the distance between the third and fourth lens groups changes, the distance between the fourth and fifth lens groups changes, the second and fourth lens groups move along the same trajectory along the optical axis, and at least the third lens group moves along the optical axis.

A zoom lens includes, in order from an object side to an image side, a lens unit Ln having the highest negative refractive power of all the following lens units, a lens unit Lm2 having positive refractive power, a lens unit Lm having negative refractive power, and a rear lens group Lp including one or more lens units and having overall positive refractive power. During zooming, a distance between every adjacent lens units varies. During focusing from an infinite distance to a minimum object distance, the lens unit Ln and the lens unit Lm move toward the object side. The focal length F.sub.Lm of the lens unit Lm and the focal length F.sub.Lm2 of the lens unit Lm2 are appropriately set.

Provided is a zoom optical system which includes, in order from an object, a first lens group having negative refractive power and other lens groups, and in which an interval between each lens group changes upon zooming, wherein the first lens group includes a first negative lens which is disposed closest to the object and has a diffractive optical element on an image side lens surface, and a positive lens disposed closer to the image than the first negative lens, and the glass material used for the positive lens satisfies the following conditions expressions: 1p35 and (g, F)0.007, where 1p denotes an Abbe number, based on the d-line, of the glass material used for the positive lens of the first lens group, and (g, F) denotes a deviation of the partial dispersion ratio of the glass material, which is used for the positive lens, from a standard line that connects a glass type A and a glass type B in a graph of which abscissa is an Abbe number d based on the d-line, and the ordinate is the partial dispersion ratio (g, F)=(ngnF)/(nFnC), with the Abbe number d and the partial dispersion ratio (g, F) of the glass type A and the glass type B being as follows: Glass type A: d=60.49, (g, F)=0.5436; glass type B: d=36.26, (g, F)=0.5828.

A zoom lens includes, in order from an object side to an image side, a first lens unit having negative refractive power, and a rear group including at least three lens units and having combined positive refractive power at a wide-angle end. A distance between adjacent lens units changes during zooming. The first lens unit includes three negative lenses consecutively arranged from the object side to the image side. Predetermined inequalities are satisfied.

A zoom lens includes a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and two or more additional lens units. In zooming, the first lens unit moves, and an interval between adjacent lens units changes. The refractive index of a negative lens A disposed on a most object side of negative lenses included in the first lens unit is higher than or equal to 1.89, and the negative lens A and a lens B disposed adjacent to an image side of the negative lens A satisfy a predetermined relationship.