The 18-200mm f/3.5-6.3 DT Telephoto Zoom Lens from Sony is a DT-series Alpha lens that has been optimized for cropped image sensors, and as a result it is not recommended for use with larger full-frame cameras. Its optics have been optimized for a small diameter image circle in order to work with the APS-C size sensor used with digital SLR cameras. When used with a digital SLR camera, the equivalent focal length for this lens is 27-300mm.
It is constructed of 15 elements in 13 groups - two of them being Extra-low Dispersion (ED) glass and another three aspherical glass elements - which all help to deliver sharp, clear photos throughout the zoom range. It has a minimum focusing distance of 1.5' and a non-rotating front-end filter diameter of 62mm, allowing you to use circular polarizing filters without difficulty.