Zoom lens and imaging apparatus

A zoom lens comprising:

• a front group that has positive refractive power as a whole;
• and
• a lens group GB disposed on an image side of the front group, wherein
• the front group and the lens group GB are arranged sequentially in a stated order from an object side,
• a magnification is changed by a change of a distance on an optical axis between adjacent lens groups,
• the front group includes at least three lens groups,
• the lens group GB includes sequentially from the image side, a negative lens component Nb, a negative lens component Nf, and a positive lens component P,
• an object-side surface of the negative lens component Nb is a concave surface,
• the lens group GB is moved to the object side in zooming from a wide-angle end to a telephoto end,
• focusing is obtained by movement of a part of the lens groups included in the front group, along the optical axis,
• a following condition expression is satisfied:
• −0.7≤(RNf+RNb)/(RNf−RNb)≤2.0 (1)
• where
• RNf represents a radius of curvature of a surface located closest to an image in the negative lens component Nf, and
• RNb represents a radius of curvature of a surface located closest to an object in the negative lens component Nb, and
• a following condition expression is satisfied:
• 0.657≤BFw/Y≤1.5 (3)
• where
• BFw represents a back focus of the zoom lens at the wide-angle end, and
• Y represents the largest image height of the zoom lens.

A zoom lens comprising:

• a front group that has positive refractive power as a whole;
• and
• a lens group GB disposed on an image side of the front group, wherein
• the front group and the lens group GB are arranged sequentially in a stated order from an object side,
• a magnification is changed by a change of a distance on an optical axis between adjacent lens groups,
• the front group includes at least three lens groups,
• the lens group GB includes sequentially from the image side, a negative lens component Nb, a negative lens component Nf, and a positive lens component P,
• an object-side surface of the negative lens component Nb is a concave surface,
• the lens group GB is moved to the object side in zooming from a wide-angle end to a telephoto end,
• focusing is obtained by movement of a part of the lens groups included in the front group, along the optical axis,
• a following condition expression is satisfied:
• −0.7≤(RNf+RNb)/(RNf−RNb)≤2.0 (1)
• where
• RNf represents a radius of curvature of a surface located closest to an image in the negative lens component Nf, and
• RNb represents a radius of curvature of a surface located closest to an object in the negative lens component Nb, and
• the positive lens component P has a double convex shape.

A zoom lens comprising:

• a front group that has positive refractive power as a whole;
• and
• a lens group GB disposed on an image side of the front group, wherein
• the front group and the lens group GB are arranged sequentially in a stated order from an object side,
• a magnification is changed by a change of a distance on an optical axis between adjacent lens groups,
• the front group includes at least three lens groups,
• the lens group GB includes sequentially from the image side, a negative lens component Nb, a negative lens component Nf, and a positive lens component P,
• an object-side surface of the negative lens component Nb is a concave surface,
• the lens group GB is moved to the object side in zooming from a wide-angle end to a telephoto end,
• focusing is obtained by movement of a part of the lens groups included in the front group, along the optical axis,
• a following condition expression is satisfied:
• −0.7≤(RNf+RNb)/(RNf−RNb)≤2.0 (1)
• where
• RNf represents a radius of curvature of a surface located closest to an image in the negative lens component Nf, and
• RNb represents a radius of curvature of a surface located closest to an object in the negative lens component Nb, and
• a following condition expression is satisfied:
• 0.5≤fP/Y≤2.7 (4)
• where
• fP represents a focal length of the positive lens component P, and
• Y represents the largest image height of the zoom lens.

A zoom lens comprising:

• a front group that has positive refractive power as a whole;
• and
• a lens group GB disposed on an image side of the front group, wherein
• the front group and the lens group GB are arranged sequentially in a stated order from an object side,
• a magnification is changed by a change of a distance on an optical axis between adjacent lens groups,
• the front group includes at least three lens groups,
• the lens group GB includes sequentially from the image side, a negative lens component Nb, a negative lens component Nf, and a positive lens component P,
• an object-side surface of the negative lens component Nb is a concave surface,
• the lens group GB is moved to the object side in zooming from a wide-angle end to a telephoto end,
• focusing is obtained by movement of a part of the lens groups included in the front group, along the optical axis,
• a following condition expression is satisfied:
• −0.7≤(RNf+RNb)/(RNf−RNb)≤2.0 (1)
• where
• RNf represents a radius of curvature of a surface located closest to an image in the negative lens component Nf, and
• RNb represents a radius of curvature of a surface located closest to an object in the negative lens component Nb, and
• a following condition expression is satisfied:
• 0.2≤RP/fw≤2.5 (6)
• where
• RP represents a radius of curvature of an object-side surface of the positive lens component P, and
• fw represents a focal length of the zoom lens at the wide-angle end.

A zoom lens comprising:

• a front group that has positive refractive power as a whole;
• and
• a lens group GB disposed on an image side of the front group, wherein
• the front group and the lens group GB are arranged sequentially in a stated order from an object side,
• a magnification is changed by a change of a distance on an optical axis between adjacent lens groups,
• the front group includes at least three lens groups,
• the lens group GB includes sequentially from the image side, a negative lens component Nb, a negative lens component Nf, and a positive lens component P,
• an object-side surface of the negative lens component Nb is a concave surface,
• the lens group GB is moved to the object side in zooming from a wide-angle end to a telephoto end,
• focusing is obtained by movement of a part of the lens groups included in the front group, along the optical axis,
• a following condition expression is satisfied:
• −0.7≤(RNf+RNb)/(RNf−RNb)≤2.0 (1)
• where
• RNf represents a radius of curvature of a surface located closest to an image in the negative lens component Nf, and
• RNb represents a radius of curvature of a surface located closest to an object in the negative lens component Nb, and
• a following condition expression is satisfied:
• 23≤νP≤45 (8)
• where
• νP represents an Abbe number of a positive lens for a d line, the positive lens being included in the positive lens component P and having the smallest Abbe number.