The dynamic 11-20mm F/2.8 Di III-A2 RXD Lens from Tamron is a fast-aperture ultra-wide-angle zoom lens for Sony E-mount APS-C mirrorless cameras. It features a fast and constant f/2.8 maximum aperture and has a compact and lightweight design. Individual elements also feature Tamron's BBAR coating, which suppresses flare and ghosting for greater contrast when working in backlit and harsh lighting conditions. A responsive RXD stepping drive motor enables quick, near-silent autofocus performance to suit stills and video. ATamron FE 11-20mm F/2.8 Di III-A RXD Lens for Sony E Mount (B060)dditionally, the f/2.8 maximum aperture produces a shallower depth-of-field that creates soft bokeh background details. Moisture-resistant construction protects the lens under inclement conditions, and a fluorine coating on the front lens element protects against dust, dirt, and smearing. Bright, constant f/2.8 maximum aperture affords consistent brightness throughout the zoom range and offers improved control over the depth of field.XLD (eXtra Low Dispersion), LD (Low Dispersion), and GM (Glass-Molded Aspherical) elements greatly reduce color fringing, chromatic aberrations, and image distortion throughout the zoom range for improved clarity and color accuracy.RXD (Rapid eXtra-silent stepping Drive) autofocus motor delivers impressively quiet, quick, and smooth focusing performance to suit both still and video applications. Designed and built with moisture-resistant construction for use in inclement conditions, plus a fluorine coating on the front lens element to protect against dust, dirt, and smearing.