The AT-X 840 AF-II model adds a built-in tripod collar that allows the lens to rotate 360x and be locked in any position and refinements in the auto focus gearing for a smoother AF. The optical design incorporates SD (APO) glass and an internal flare cutting mechanism, which removes unnecessary light (flare) to render clean sharp images. Another highly functional feature of the AT-X 840 AF-II is the zoom lock, which secures the zoom lens in its most compact position at 80 mm.Using the included bayonet lens hood further eliminates unwanted flare. All metal barrel construction, chrome plated brass mount plate and SD glass all combine to create an AT-X lens built for travel photography.