Zoom lens and image capturing apparatus

1. A zoom lens comprising: in order from an object side to an image side,

a first lens group having negative refractive power;

a second lens group having positive refractive power;

a third lens group having negative refractive power; and

a fourth lens group having positive refractive power,

wherein, in zooming from a wide-angle end to a telescopic end, the first lens group moves to the object side in a manner that a distance toward the second lens group narrows, and a distance between the third lens group and the fourth lens group widens,

wherein the third lens group includes a single lens or a single cemented lens, and

wherein the following conditional expressions (a) and (b) are satisfied,

Δ m 3/( fw×ft ) 1/2 <0.3  conditional expression (a):

d 23_max/( fw×ft ) 1/2 <0.5  conditional expression (b):

where

Δm3: a variation amount of a distance between the second lens group and the third lens group in varying magnification, and

d23_max: a maximum value of the distance between the second lens group and the third lens group in varying magnification.

2. The zoom lens according to claim 1 ,

wherein the second lens group includes, in order from the object side, four lenses of a first positive lens, a second positive lens, a negative lens and a third positive lens, and

wherein the second positive lens and the negative lens are joined with each other.

3. The zoom lens according to claim 1 ,

wherein the third lens group satisfies the following conditional expression (c),

−3< f 3 g/ft<− 0.8  conditional expression (c):

where

f3g: a focal length of the third lens group, and

ft: a system focal length at the telescopic end.

4. The zoom lens according to claim 2 ,

wherein vibration isolation is performed by moving the third positive lens or the third lens group perpendicularly to an optical axis.

5. The zoom lens according to claim 1 , comprising:

an aperture stop disposed on the second lens group or between the second lens group and the third lens group; and

a light shielding member shielding a circumferential light ray on a part of the third lens group at the wide-angle end,

wherein the following conditional expression (d) is satisfied,

L×Fno — w /( fw×ft ) 1/2 <2.5  conditional expression (d):

where

L: a distance along an optical axis between the aperture stop and the light shielding member at the wide-angle end,

Fno_w: an F value at the wide-angle end,

fw: a system focal length at the wide-angle end, and

ft: a system focal length at the telescopic end.

6. The zoom lens according to claim 2 ,

wherein each of the third positive lens and the third lens group includes a single lens made of a resin.

7. An image capturing apparatus comprising:

a zoom lens including, in order from an object side to an image side,

a first lens group having negative refractive power,

a second lens group having positive refractive power,

a third lens group having negative refractive power, and

a fourth lens group having positive refractive power; and

an image sensor converting an optical image formed by the zoom lens into an electric signal,

wherein, in zooming from a wide-angle end to a telescopic end, the first lens group moves to the object side in a manner that a distance toward the second lens group narrows, and a distance between the third lens group and the fourth lens group widens,

wherein the third lens group includes a single lens or a single cemented lens, and

wherein the following conditional expressions (a) and (b) are satisfied,

Δ m 3/( fw×ft ) 1/2 <0.3  conditional expression (a):

d 23_max/( fw×ft ) 1/2 <0.5  conditional expression (b):

where

Δm3: a variation amount of a distance between the second lens group and the third lens group in varying magnification, and

d23_max: a maximum value of the distance between the second lens group and the third lens group in varying magnification.