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.
Note: Not compatible with 35mm or "full-frame" digital SLR cameras (e.g. A900, film cameras)
APS-C 35mm Equivalent: 27-300mm
This 18-200mm lens has an 11x zoom factor, but its viewing angle becomes the 35mm equivalent of a 27-300mm lens when attached to the cropped APS-C cameras it was designed for.
Aperture Range: f/3.5-40
With a maximum aperture of f/3.5 and minimum of f/40 this lens' high speed means you can capture images in darker conditions using faster shutter speeds and lower ISO sensitivity.
Optimized For APS-C Size / DT-Format Alpha & Minolta DSLRs
Intended for smaller, cropped Sony Alpha cameras, DT lenses employ an optical system that is specifically designed for digital cameras which incorporate an APS-C size image sensor.
2x Extra-Low Dispersion (ED) Elements
To reduce chromatic aberrations, most noticeable when zoomed all the way in, the extra-low dispersion glass corrects for certain wavelengths of light - producing sharper images with truer colors.
3x Aspherical Glass Lens Elements
These precision lens elements correct distortion for sharper, more visually accurate images across the entire zoom range of the lens.
Internal lens elements move, so the overall length does not change, creating a lens that focuses more quickly and doesn't change balance.
7x Circular Aperture Blades
Circular aperture blades produce smooth, rounded bokeh background effects when capturing spot-light sources in your pictures. Because the aperture blades form a near circle at the wide openings used for low-light shots, spot-light sources have a pleasing circular defocused effect.
Filter Diameter: 62mm
The 62mm front filter thread does not rotate, allowing rotating polarizing filters to be used.