Patent ID: 7289274

Claim:
A telescopic 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 and said positive fourth lens group remain stationary, said negative second lens group moves toward the image, and said positive third lens group first moves toward an image and thereafter moves toward the object; wherein said positive first lens group comprises a positive front sub-lens group and a positive rear sub-lens group which are separated at a maximum air-distance therebetween; wherein said positive rear sub-lens group functions as a focusing lens group; wherein said positive rear sub-lens group comprises a negative meniscus lens element having the convex surface facing toward the object, and a positive lens element having a convex surface facing toward the object, in this order from the object; wherein said positive rear sub-lens group satisfies the following condition: 2.7< flR/ft< 3.5 wherein flR designates the focal length of said positive rear sub-lens group; and ft designates the focal length of the entire telescopic zoom lens system at the long focal length extremity.