Zoom lens and imaging apparatus

1. A zoom lens consisting of, in order from an object side:

a first lens group that has a positive refractive power;

a second lens group that has a negative refractive power;

a third lens group that has a positive refractive power;

a diaphragm; and

a fourth lens group,

wherein during zooming, the first lens group and the fourth lens group remain stationary with respect to an image plane, and the second lens group and the third lens group move so as to have a different relative spacing therebetween in an optical axis direction,

wherein the first lens group consists of, in order from the object side, a cemented lens that is formed by cementing a first lens, which has a negative refractive power and has a meniscus shape convex toward the object side, and a second lens which has a positive refractive power, a third lens that has a positive refractive power, and a fourth lens that has a negative refractive power,

wherein the following conditional expression (1) is satisfied,

−0.8< f 1 a/f 1 b< 0  (1),

where f1a is a composite focal length of the first lens, the second lens, and the third lens, and

f1b is a focal length of the fourth lens, and

wherein lens spacing in the fourth lens group does not change during zooming.

2. The zoom lens according to claim 1 , wherein the following conditional expression (2) is satisfied,

−0.01<θ gF 2−θ gF 1<0.015  (2),

where θgF1 is a partial dispersion ratio of the first lens between the g line and the F line, and

θgF2 is a partial dispersion ratio of the second lens between the g line and the F line.

3. The zoom lens according to claim 1 , wherein the following conditional expression (3) is satisfied,

5<ν d 2−ν d 1<40  (3),

where νd1 is an Abbe number of the first lens on the basis of a d-line, and

νd2 is an Abbe number of the second lens on the basis of the d-line.

4. The zoom lens according to claim 2 , wherein the following conditional expression (3) is satisfied,

5<ν d 2−ν d 1<40  (3),

where νd1 is an Abbe number of the first lens on the basis of a d-line, and

νd2 is an Abbe number of the second lens on the basis of the d-line.

5. The zoom lens according to claim 1 , wherein during zooming from a wide-angle end to a telephoto end, a spacing between the third lens group and the fourth lens group constantly increases, and the second lens group and the third lens group simultaneously pass through a point at which respective lateral magnifications thereof are −1 times.

6. The zoom lens according to claim 1 , wherein the following conditional expression (4) is satisfied,

2.5< fT/f 1<4.5  (4),

where fT is a focal length of the whole system at the telephoto end, and

f1 is a focal length of the first lens group.

7. The zoom lens according to claim 1 , wherein the following conditional expression (5) is satisfied,

−50< fT/f 2<−10  (5),

where fT is a focal length of the whole system at the telephoto end, and

f2 is a focal length of the second lens group.

8. The zoom lens according to claim 1 , wherein the following conditional expression (6) is satisfied,

5< fT/f 3<30  (6),

where fT is a focal length of the whole system at the telephoto end, and

f3 is a focal length of the third lens group.

9. The zoom lens according to claim 1 , wherein the following conditional expression (7) is satisfied,

−15< fT/f 4<3  (7),

where fT is a focal length of the whole system at the telephoto end, and

f4 is a focal length of the fourth lens group.

10. The zoom lens according to claim 1 , wherein the fourth lens group has a negative refractive power.

11. The zoom lens according to claim 1 , wherein the fourth lens group has a positive refractive power.

12. The zoom lens according to claim 1 , wherein focusing is performed by moving the entire first lens group.

13. The zoom lens according to claim 1 , wherein the following conditional expression (1-1) is satisfied

−0.7< f 1 a/f 1 b<− 0.2  (1-1)

14. The zoom lens according to claim 1 , wherein the following conditional expression (2-1) is satisfied,

−0.008<θ gF 2−θ gF 1<0.01  (2-1),

where θgF1 is a partial dispersion ratio of the first lens between the g line and the F line, and

θgF2 is a partial dispersion ratio of the second lens between the g line and the F line.

15. The zoom lens according to claim 1 , wherein the following conditional expression (3-1) is satisfied,

7<ν d 2−ν d 1<35  (3-1),

where νd1 is an Abbe number of the first lens on the basis of the d-line, and

νd2 is an Abbe number of the second lens on the basis of the d-line.

16. The zoom lens according to claim 1 , wherein the following conditional expression (4-1) is satisfied,

2.8< fT/f 1<4  (4-1),

where fT is a focal length of the whole system at the telephoto end, and

f1 is a focal length of the first lens group.

17. The zoom lens according to claim 1 , wherein the following conditional expression (5-1) is satisfied,

−40< fT/f 2<−20  (5-1),

where fT is a focal length of the whole system at the telephoto end, and

f2 is a focal length of the second lens group.

18. The zoom lens according to claim 1 , wherein the following conditional expression (6-1) is satisfied,

7< fT/f 3<25  (6-1),

where fT is a focal length of the whole system at the telephoto end, and

f3 is a focal length of the third lens group.

19. The zoom lens according to claim 1 , wherein the following conditional expression (7-1) is satisfied,

−12< fT/f 4<2  (7-1),

where fT is a focal length of the whole system at the telephoto end, and

f4 is a focal length of the fourth lens group.

20. An imaging apparatus comprising the zoom lens according to claim 1 .