The 55-200mm f/4.0-5.6 DT Alpha A-Mount Telephoto Zoom Lens from Sony is a DT-series Sony 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. It's 55-200mm focal length is the 35mm equivalent of a long 82.5-300mm telephoto lens. It is constructed of 13 elements in 9 groups, as well as Extra-low Dispersion (ED) glass, which all help to deliver sharp, clear photos throughout the zoom range. It has a minimum focusing distance of 3.2' and a front-end filter diameter of 55mm.
The lens has effectively an 82.5-300mm focal length when used with the APS-C sized cameras it is designed for, and its aperture varies depending on the focal length you choose. It will slowly increase from f/4.0 to f/5.6, or f/32 to 45, as you increase the amount of zoom. The 7x circular aperture blades produce smooth, out of focus background effects, and the front focus Smooth Autofocus Motor (SAM) moves the focusing lens elements directly, helping to assure quick, yet smooth, AF response.
82.5-300mm (35mm Equivalent) 3.5x Zoom Lens
Having been built for cropped image sensors, you can easily capture close-ups with this far-reaching zoom lens. Shoot with a wide range of focal lengths ranging from the 35mm equivalent of 82.5mm all the way up to 300mm, without having to swap lenses.
Aperture Range: f/4.0-45
In addition to the zoom range, the lens' aperture range also increases along with the focal length, from f/4.0 to 5.6 at the wide end, and f/32 to 45 at the narrow end.
Optimized For APS-C Size / DT-Format Alpha & Minolta DSLRs
Designed specifically for APS-C sized sensors, used in many Sony Alpha DSLR cameras, this lens can be more compact than it otherwise would be if built for a full-frame camera. It is recommended only for use with DT-format Alpha & Minolta cropped SLR cameras.
Smooth Autofocus Motor (SAM)
The built-in Smooth Autofocus Motor (SAM) eliminates the need to use a mechanical coupling system in the camera body. Instead of transferring autofocus (AF) drive power and control signals to the lens, the AF control signals are sent from the camera body to the lens-mounted SAM unit. This drives the focusing lens group directly, providing smoother and more precise autofocus.
Extra-Low Dispersion (ED) Glass
To reduce chromatic aberrations, most noticeable when zoomed all the way in to the 300mm equivalent focal length, the extra-low dispersion glass corrects for certain wavelengths of light - producing sharper images with truer colors.
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.
SteadyShot INSIDE In-Camera Image Stabilization
Because Sony's Alpha DSLR cameras have SteadyShot INSIDE image stabilization built-in, the lenses attached to them don't require the added bulk. This leaves the lens lighter and more compact without the need for the added mechanics.