The Samyang 14mm T3.1 ED AS IF UMC VDSLR is an ultra-wide angle lens suitable for taking stills & video footage on DSLR cameras, as well as professional camcorders. The stated aperture of T3.1 refers to the actual light transmission of the lens & is particularly important in the film industry where light readings are normally made manually. This highly professional lens features gearing on the focus & aperture rings to allow follow focus & aperture control from a professional camera rig. The aperture ring is also stepless for smooth & continuous adjustment. Focus distance & aperture settings are clearly marked on the side of the lens barrel to allow easy reference when mounted on a tripod. With 14 elements in 10 groups & Ultra Multi Coatings, the Samyang 14mm is designed to produce life-like images full of contrast. This lens has no autofocus (AF) motor & is a Manual focus only lens.