Sony's fastest A-mount APS-C standard zoom - constant f/2.8 across 16-50mm, SSM focus, 577g.
The Sony DT 16-50mm f/2.8 SSM is a constant-aperture standard zoom for APS-C Sony A-mount bodies, announced in August 2011 and sold as the kit lens for the SLT-A65 and SLT-A77. The DT designation marks it as an APS-C lens, and it was the fastest standard zoom Sony offered for the crop-sensor Alpha line. It was discontinued as Sony wound the A-mount system down in favour of E-mount.
A 16-50mm zoom holding f/2.8 across the whole range, closing to f/22, with a seven-blade aperture. Minimum focus is 30cm at any focal length for a maximum magnification of 0.2x, the filter thread is 72mm, and the lens measures 81mm by 88mm and weighs 577g. Focus is driven by Sony's Super Sonic wave Motor, which allows direct manual override, and the barrel does not rotate during focusing.
The 24-75mm equivalent range covers most general shooting, and the constant f/2.8 is what separates it from the 18-55mm and 16-105mm kit zooms it sat above - a stop and a half more light at the long end, and consistent exposure through the zoom range. The SSM focus drive is quieter and faster than the screw-drive lenses that make up much of the A-mount catalogue, which matters on the SLT bodies it was designed around.
This lens holds its value better than most A-mount glass because there is no direct replacement for it on the system. Check the zoom ring for the play that develops with heavy use, confirm the SSM motor drives smoothly and silently through the full range rather than hunting, and inspect the front element, which sits close to the filter thread and picks up marks. Buyers moving to E-mount should note that phase-detect autofocus with an LA-EA adapter is not equivalent to native performance.