1. A zoom lens, comprising, in an order from an object side to an image side:
- 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; and
- a fourth lens group having a positive refractive power, wherein:
- during power variation from a wide angle end to a telephoto end, each group is moved in an optical axis direction, and a following conditional expression (1) is satisfied:
- description="In-line Formulae" end="lead"−5
- where:
- f1 is a focal length of the first lens group; and
- f4 is a focal length of the fourth lens group.
2. The zoom lens according to claim 1, wherein a following conditional expression (2) is satisfied:
- description="In-line Formulae" end="lead"−1.7
where:
D3: an optical path diameter on an on-axis bundle on a surface closest to the object side of the third lens group at the telephoto end.
3. The zoom lens according to claim 1, wherein a whole of the first lens group is moved to the optical axis direction to perform focusing on a close subject.
4. The zoom lens according to claim 1, wherein:
- the first lens group is configured with an object-side sub-group positioned on the object side and an image-plane-side sub-group positioned on an image-plane side, and
- the image-plane-side sub-group is moved to perform focusing on a close subject.
5. The zoom lens according to claim 4, wherein:
- a following conditional expression (3) is satisfied:
- description="In-line Formulae" end="lead"0.15
where:
f11 is a focal length of the object-side sub-group in the first lens group; and
f12 is a focal length of the image-plane-side sub-group in the first lens group.
6. The zoom lens according to claim 1, comprising an aspheric surface disposed, on a surface closest to the object side of the first lens group, such that the further away from the optical axis, the stronger a positive refractive force.
7. An imaging apparatus, comprising:
- a zoom lens; and
- an image sensor for converting an optical image formed by the zoom lens into an electric signal, wherein:
- the zoom lens includes, in an order from an object side to an image side:
- 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; and
- a fourth lens group having a positive refractive power are aligned, and
- during power variation from a wide angle end to a telephoto end, each group is moved in an optical axis direction, and a following conditional expression (1) is satisfied:
- description="In-line Formulae" end="lead"−5
- where:
- f1 is a focal length of the first lens group; and
- f4 is a focal length of the fourth lens group.
