Standard zoom lens system

1. A standard zoom lens system comprises a positive first lens group, a negative second lens group, a positive third lens group and a positive fourth lens group, in this order from an object,

wherein upon zooming from the short focal length extremity to the long focal length extremity, said positive first lens group, said positive third lens group and said positive fourth lens group move toward the object, and said negative second lens group moves toward an image and thereafter moves toward the object;

wherein said positive first lens group consists of a negative lens element and a positive lens element; and

wherein said standard zoom lens system satisfies the following conditions:

7.5 <f 1 /|f 2|<9.5

3.0 <f 1 /f 3 <5.0

wherein

f1 designates the focal length of said positive first lens group;

f2 designates the focal length of said negative second lens group; and

f3 designates the focal length of said positive third lens group.

2. The standard zoom lens system according to claim 1 , satisfying the following condition:

7.0< f 1 /fw< 10.0

wherein

f1 designates the focal length of said positive first lens group; and

fw designates the focal length of said entire standard zoom lens system at the short focal length extremity.

3. The standard zoom lens system according to claim 1 , wherein said negative lens element and said positive lens element of said positive first lens group are cemented to each other.

4. The standard zoom lens system according to claim 1 , wherein said negative second lens group comprises two negative lens elements and a positive lens element.

5. The standard zoom lens system according to claim 4 , wherein said negative second lens group comprises a negative meniscus lens element having the convex surface facing toward the object, a negative lens element having a concave surface facing toward the image, and a positive lens element having a convex surface facing toward the object, in this order from the object.

6. The standard zoom lens system according to claim 4 , satisfying the following condition:

0.7 <| f 2 |/fw < 1.2

wherein

f2 designates the focal length of said negative second lens group; and

fw designates the focal length of said entire standard zoom lens system at the short focal length extremity.

7. The standard zoom lens system according to claim 4 , satisfying the following condition:

1.68<Nn<1.79

wherein

Nn designates the refractive index of the d-line of each negative lens element in the negative second lens group.

8. The standard zoom lens system according to claim 1 , wherein said positive fourth lens group comprises one of a positive aspherical lens element and a negative aspherical lens element, and cemented lens elements having a positive lens element and a negative lens element.

9. The standard zoom lens system according to claim 1 , satisfying the following condition:

1.0 <f 4 /f 3 <3.0

wherein

f4 designates the focal length of said positive fourth lens group; and

f3 designates the focal length of said positive third lens group.

10. The standard zoom lens system according to claim 1 , satisfying the following condition:

0.6 <|f 12 w|/f 34 w < 0.8

wherein

f12w designates the combined focal length of the positive first lens group and the negative second lens group at the short focal length extremity; and

f34w designates the combined focal length of said positive third lens group and said positive fourth lens group at the short focal length extremity.

11. A standard zoom lens system comprises a positive first lens group, a negative second lens group, a positive third lens group and a positive fourth lens group, in this order from an object,

wherein upon zooming from the short focal length extremity to the long focal length extremity, said positive first lens group, said positive third lens group and said positive fourth lens group move toward the object, and said negative second lens group moves toward an image and thereafter moves toward the object;

wherein said positive first lens group comprises a negative lens element and a positive lens element;

wherein said negative second lens group comprises two negative lens elements and a positive lens element; and

wherein said standard zoom lens system satisfies the following conditions:

7.0 <f 1 /fw< 10.0

1.68<Nn<1.79

wherein

f1 designates the focal length of said positive first lens group;

fw designates the focal length of said entire standard zoom lens system at the short focal length extremity; and

Nn designates the refractive index of the d-line of each negative lens element in the negative second lens group.

12. The standard zoom lens system according to claim 11 , wherein said negative lens element and said positive lens element of said positive first lens group are cemented to each other.

13. The standard zoom lens system according to claim 11 , wherein said negative second lens group comprises a negative meniscus lens element having the convex surface facing toward the object, a negative lens element having a concave surface facing toward the image, and a positive lens element having a convex surface facing toward the object, in this order from the object.

14. The standard zoom lens system according to claim 11 , satisfying the following condition:

0.7 <1 |f 2|/ fw < 1.2

wherein

f2 designates the focal length of said negative second lens group; and

fw designates the focal length of said entire standard zoom lens system at the short focal length extremity.

15. The standard zoom lens system according to claim 11 , wherein said positive third lens group comprises a positive lens element, and cemented lens elements having a positive lens element and a negative lens element.

16. The standard zoom lens system according to claim 11 , wherein said positive fourth lens group comprises one of a positive aspherical lens element and a negative aspherical lens element, and cemented lens elements having a positive lens element and a negative lens element.

17. The standard zoom lens system according to claim 11 , satisfying the following condition:

1.0 <f 4/ f 3 <3.0

wherein

f4 designates the focal length of said positive fourth lens group; and

f3 designates the focal length of said positive third lens group.

18. The standard zoom lens system according to claim 11 , satisfying the following condition:

0.6 <|f 12 w|/f 34 w < 0.8

wherein

f12w designates the combined focal length of the positive first lens group and the negative second lens group at the short focal length extremity; and

f34w designates the combined focal length of said positive third lens group and said positive fourth lens group at the short focal length extremity.

19. A standard zoom lens system comprises a positive first lens group, a negative second lens group, a positive third lens group and a positive fourth lens group, in this order from an object,

wherein upon zooming from the short focal length extremity to the long focal length extremity, said positive first lens group, said positive third lens group and said positive fourth lens group move toward the object, and said negative second lens group moves toward an image and thereafter moves toward the object;

wherein said positive first lens group comprises a negative lens element and a positive lens element;

wherein said positive third lens group comprises a positive lens element, and cemented lens elements having a positive lens element and a negative lens element; and

wherein said standard zoom lens system satisfies the following conditions:

7.5 <f 1 /|f 2|<9.5

3.0 <f 1 /f 3 <5.0

wherein

f1 designates the focal length of said positive first lens group;

f2 designates the focal length of said negative second lens group; and

f3 designates the focal length of said positive third lens group.