| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-performance zoom lens system which is used for a large aperture standard zoom lens whose maximum aperture is approximately 2.8 at the wide angle end and varies with zooming, and which is equipped with an anti-shake mechanism and an inner focusing mechanism and yet achieves a sufficiently compact size and a reduced minimum shooting distance.SOLUTION: A zoom lens system comprises a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. The third lens group comprises a 3A lens group having a positive refractive power and a 3B lens group having a negative or positive refractive power. When zooming from the wide angel end to the telephoto end, the aperture stop follows a different locus from that of each lens group. When in an anti-shake motion, an anti-shake lens comprising a single negative lens moves in a direction substantially perpendicular to the optical axis. The anti-shake lens is the whole or a part of the 3B lens group. The zoom lens satisfies predefined conditional expressions. |
