This is a light weight,compact telephoto lens that was designed for mobility. Two UD lenses thoroughly eliminate secondary spectrum. The new rear focus design which reduces the overall weight of the moving lens elements and improves focusing precision also compensates for aberrations. The lens boasts excellent sharp, clear imaging performance at all focusing distances. The quick and quiet AF which uses a ring-type USM and the fine-tuned physical balance of the lens make operation a delight. It is equipped with a large separate hood which blocks out light very effectively. It is compatible with an optional detachable tripod collar, which provides a stable support and can be switched smoothly from vertical to horizontal positions and vice-versa.