| 摘要 |
PROBLEM TO BE SOLVED: To provide a negative-positive-positive three-group zoom lens system which offers reduced size, brightness with an F number of 2.8 or less, a widened view angle with a half view angle of 35 degrees or greater, and a magnification ratio of approximately 5x, and which is well corrected for off-axial aberrations and has appropriately set sensitivity to eccentricity in a second lens group.SOLUTION: A zoom lens system comprises, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having positive refractive power. At the time of zooming, the first lens group G1 and second lens group G2 move toward the object side, and the third lens group G3 moves toward the image side. The second lens group G2 comprises four lenses, of which a lens located on the most image side has at least one aspherical surface, and satisfies conditional expressions: (1) 2.1<ft/f2<2.7, (2) |f2/f24|<0.3, where ft represents a focal length of the entire system at a long focal length end, f2 represents a focal length of the second lens group G2, and f24 represents a focal length of a most image side lens of the second lens group G2. |
