At three and a half pounds, this lens is very large: in practice, you end up attaching the camera body to the lens, rather than attaching the lens to the camera body. The 150mm ƒ/2 is listed in the "Super High Quality" lineup, developed for more advanced optical/precision technology and exquisite picture quality. It's also listed as being dust and splash-proof, to allow usage in harsh conditions. The lens itself is comprised of 11 elements in 9 groups, with one ED ("extra-low dispersion") lens element and one Super-ED Available to offer sharper, higher-contrast imaging performance. Available for around $2,200. Read the whole test here