Standard zoom lens system

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

wherein upon zooming from the short focal length extremity to the long focal length extremity, the distance between said negative first lens group and said positive second lens group decreases, and the distance between said positive second lens group and said positive third lens group increases;

wherein said negative first lens group comprises a negative lens element and a positive lens element, in this order from the object;

wherein the most image-side surface of the positive second lens group comprises a concave surface; and

wherein said standard zoom lens system satisfies the following conditions:

0.15 <Rs/fT< 0.173

wherein

Rs designates the radius of curvature of the most image-side surface of said positive second lens group (Rs>0); and

fT designates the focal length of said entire standard zoom lens system at the long focal length extremity when an object at an infinite distance is in an in-focus state; and

1.65<NP2

wherein

NP2 designates the refractive index of the d-line of the most object-side positive lens element of said positive second lens group;

wherein said positive lens element of said negative first lens group comprises a plastic lens element having at least one aspherical surface.

2. The standard zoom lens system according to claim 1 , wherein said positive second lens group comprises a biconvex positive lens element, and cemented lens elements having a positive lens element and a negative lens element, in this order from the object.

3. A camera having said standard zoom lens system according to claim 2 satisfies the following condition:

t 1/ Y max<1.2

wherein

t1 designates the distance from the most object-side surface to the most image-side surface of said negative first lens group; and

Ymax designates the maximum image height at the image plane on which an image through said entire standard zoom lens system is formed.

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

45<νp

wherein

νp designates the Abbe number of the most object-side positive lens element of said positive second lens group.

5. A camera having said standard zoom lens system according to claim 4 satisfies the following condition:

t 1 /Y max<1.2

wherein

t1 designates the distance from the most object-side surface to the most image-side surface of said negative first lens group; and

Ymax designates the maximum image height at the image plane on which an image through said entire standard zoom lens system is formed.

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

−1.0 <f 1/ f 1 p<− 0.3

wherein

f1<0;

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

f1p designates the focal length of said positive plastic lens element of said negative first lens group.

7. A camera having said standard zoom lens system according to claim 6 satisfies the following condition:

t 1/ Y max<1.2

wherein

t1 designates the distance from the most object-side surface to the most image-side surface of said negative first lens group; and

Ymax designates the maximum image height at the image plane on which an image through said entire standard zoom lens system is formed.

8. The standard zoom lens system according to claim 1 , wherein said positive third lens group functions as a focusing lens group which is movable along the optical axis with respect to an object at a close-distance.

9. A camera having said standard zoom lens system according to claim 8 satisfies the following condition:

t 1 /Y max<1.2

wherein

t1 designates the distance from the most object-side surface to the most image-side surface of said negative first lens group; and

Ymax designates the maximum image height at the image plane on which an image through said entire standard zoom lens system is formed.

10. The standard zoom lens system according to claim 1 , wherein said positive third lens group comprises a biconvex positive plastic lens element having at least one aspherical surface.

11. A camera having said standard zoom lens system according to claim 10 satisfies the following condition:

t 1 /Y max<1.2

wherein

t1 designates the distance from the most object-side surface to the most image-side surface of said negative first lens group; and

Ymax designates the maximum image height at the image plane on which an image through said entire standard zoom lens system is formed.

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

0.6< f 2/ f 3 p< 1.0

wherein

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

f3p designates the focal length of said biconvex positive plastic lens element of said positive third lens group.

13. A camera having said standard zoom lens system according to claim 12 satisfies the following condition:

t 1 /Y max<1.2

wherein

t1 designates the distance from the most object-side surface to the most image-side surface of said negative first lens group; and

Ymax designates the maximum image height at the image plane on which an image through said entire standard zoom lens system is formed.

14. The standard zoom lens system according to claim 1 , wherein said positive third lens group is arranged to move monotonically toward the image upon zooming from the short focal length extremity to the long focal length extremity; and

wherein said standard zoom lens system satisfies the following condition:

0.05<log( m 3 t/m 3 w )/log( fT/fW )<0.3

wherein

fT designates the focal length of said entire standard zoom lens system at the long focal length extremity when an object at an infinite distance is in an in-focus state;

fW designates the focal length of said entire standard zoom lens system at the short focal length extremity when an object at an infinite distance is in an in-focus state;

m3t designates a magnification of said positive third lens group at the long focal length extremity when an object at an infinite distance is in an in-focus state; and

m3W designates a magnification of said positive third lens group at the short focal length extremity when an object at an infinite distance is in an in-focus state.

15. A camera having said standard zoom lens system according to claim 14 satisfies the following condition:

t 1/ Y max<1.2

wherein

t1 designates the distance from the most object-side surface to the most image-side surface of said negative first lens group; and

Ymax designates the maximum image height at the image plane on which an image through said entire standard zoom lens system is formed.

16. The standard zoom lens system according to claim 1 , wherein in said positive second lens group, each lens surface of the most object-side positive lens element comprises an aspherical surface on which the curvature becomes gentler from the central portion toward the peripheral portion, compared to paraxial spherical surface of the aspherical surface.

17. A camera having said standard zoom lens system according to claim 16 satisfies the following condition:

t 1/ Y max<1.2

wherein

t1 designates the distance from the most object-side surface to the most image-side surface of said negative first lens group; and

Ymax designates the maximum image height at the image plane on which an image through said entire standard zoom lens system is formed.

18. A camera having said standard zoom lens system according to claim 1 satisfies the following condition:

t 1/ Y max<1.2

wherein

t1 designates the distance from the most object-side surface to the most image-side surface of said negative first lens group; and

Ymax designates the maximum image height at the image plane on which an image through said entire standard zoom lens system is formed.