and A77 cameras, the Sony 16-50 ƒ/2.8 DT is an APS-C compatible lens with a maximum aperture setting of ƒ/2.8 regardless of the focal length selected. Mounted on a camera body with an APS-C sensor, the lens will produce an effective field of view of approximately 24-75mm. The lens accepts a petal-shaped hood, but it's not clear at the time of writing whether it is included with the lens. The lens accepts 72mm filters, and is scheduled to be available for approximately $700 in October 2011.Sharpness
The Sony 16-50mm ƒ/2.8 produced some very sharp images, perhaps slightly sharper in the wide angle compared to telephoto. At 16mm and ƒ/2.8, the lens provides very good corner to corner sharpness, approaching tack-sharp levels in the center of the frame. Stopped down to ƒ/4, it's as sharp as sharp gets, with just a touch of softness in the corners. There's no appreciable gain stopping down to ƒ/5.6, and diffraction limiting seems to set in at ƒ/8 where there's a slight overall reduction in sharpness. This softness continues from ƒ/11 - ƒ/16, and finally ƒ/22, where it becomes quite soft indeed.
Zoomed in to 50mm, the lens is somewhat soft at ƒ/2.8, echoing the de-centering we noted at 35mm; again, stop down to ƒ/4, and the problem goes away. At 50mm and ƒ/4 we're seeing almost identical results for sharpness as we found at 35mm, and this trend continues through to ƒ/22. It's interesting to note that fully stopped-down performance (ƒ/22) is best at the 50mm setting.
Chromatic Aberration
The Sony 16-50mm ƒ/2.8 produces some odd results for chromatic aberration. Happily, the lens' best performance occurs where it's most likely to be used - at ƒ/2.8. Between 16mm and 35mm, chromatic aberration increases as the lens is stopped down, becoming more prominent and showing as magenta-green fringing in areas of high contrast. At 50mm, this trend reverses abruptly; now the lens shows a standard amount of chromatic aberration at ƒ/2.8, and improves as it's stopped down. By ƒ/5.6 at 50mm, there is very little CA to speak of.
It's worth noting that while we didn't test the lens on the new A77 body. In his preview of that camera body, Shawn Barnett noted that the camera seemed to correct these levels of chromatic aberration. You may want to read his preview of the A77, here.
Shading (''Vignetting'')
Corner shading is fairly light on the 16-50mm ƒ/2.8. It's most prominent at 16mm, where there is always some level of shading; the worst offender is at 16mm and ƒ/2.8, where we note corners which are upwards of 3/4 EV darker than the center. At any other setting, it's less than that; at any other focal length, the only setting which produces any corner shading of note is 16mm, where you'll see corners that are a half-stop darker than the center.
Distortion
The Sony 16-50mm ƒ/2.8 shows some fairly prominent barrel distortion at 16mm (a full +1% in the corners), but this reduces gracefully as the lens is zoomed in. There is a point of parity around 30mm where there is neither barrel nor pincushion distortion. At 50mm, we note some very light pincushion distortion in the corners; about -0.1%.
Autofocus Operation
On the Sony A350 body, the lens took well under one second to focus from closest focus to infinity, so it is very fast indeed. Small focus changes happen nearly instantly and silently. The front element doesn't rotate, making life easier for polarizer users.
Macro
The lens isn't made for macro, but offers a usable 0.2x magnification ratio, at a close-focusing distance of 30cm (one foot).
Build Quality and Handling
The lens barrel is a plastic type with a roughly-textured, black matte finish. At just over 20 oz in weight, the lens is fairly heavy. The lens mount is metal, while the 72mm filter threads are plastic. The lens offers a toggle switch to control focus on the lens (AF / MF), as well as a switch to lock the lens in its shortest focal length of 16mm. A distance scale is present under a clear plastic window, marked in feet and meters, but without a depth-of-field scale or infrared index.
The zoom ring is the larger of the two, 3/4 of an inch in width and composed of rubber with large raised ribs. The ring offers about 80 degrees of turning action to increase the focal length from 16mm to 50mm. While there is a zoom lock switch present, our sample of the lens didn't exhibit any signs of zoom creep, though as the lens is worked in, that could change. There is some lens extension as the lens is zoomed in; the lens extends by about one inch, making its total overall length at that point four and a half inches.
The focusing ring is also composed of rubber, 1/2 inch wide with large raised ribs. The ring offers smooth manual focusing, with soft stops at the close-focus and infinity focus ends (the lens will continue to turn, but an increase in resistance lets you know you can't focus any further).
The ALC-SH117 lens hood is a petal-shaped design that attaches via the bayonet mount. When attached, the hood adds about two inches of additional length. The hood can be reversed for storage on the lens.
Alternatives
Sony 16-80mm ƒ/3.5-4.5 DT Carl Zeiss Vario-Sonnar T* ~$750
While the Sony 16-80mm offers slightly more reach, it does so by offering a variable aperture; some people will value the constant ƒ/2.8 aperture of the 16-50mm. The 16-50mm offers slightly sharper performance in some focal lengths, the 16-80mm is sharper in others, but the performance of the 16-50mm is probably more consistent overall.
Sony 16-105mm ƒ/3.5-5.6 DT ~$600
Slightly less expensive than the Sony 16-50mm, the 16-105mm offers much more telephoto range, with the trade-off of a variable aperture. Sharpness results are very good, with a notable exception at 50mm (which may or may not be present in all copies of this lens).
Tamron SP AF 17-50mm ƒ/2.8 XR Di II LD Aspherical IF ~$460
The Tamron 17-50mm was one of the first lenses to appear in this focal length, and offers a similar experience to the Sony 16-50mm. The Sony is somewhat sharper, but without in-camera correction, the Tamron provides better results for chromatic aberration and corner shading. Note that the newer VC version of the Tamron isn't available in the Sony mount, and you wouldn't want it anyway; stabilization is built-in to Sony cameras.
Sigma 17-50mm ƒ/2.8 EX DC OS HSM ~$670
We haven't yet tested Sigma's offering in this category, but it's available in the Sony mount. It offers Sigma's OS technology, which Sigma indicates you shouldn't use at the same time as the built-in stabilization of the camera.
The Sony 16-50mm ƒ/2.8 DT presents itself as a capable walk-around zoom lens; mated with the newer A65 or A77 bodies, which appear to correct its slight issues with chromatic aberration, the combination works to produce excellent photographs.