The Sony FE 28-70mm F3.5-5.6 OSS ($499.99 list)($398.00 at Amazon) is the first zoom lens available for Sony's full-frame mirrorless camera system. It has the same limitations as most kit lenses, including some very noticeable distortion and soft edges at wider apertures. It's a decent starter lens, but if you can forgo a zoom until its February release, the Zeiss Vario-Tessar T* FE 24-70mm F4 ZA OSS ($1,199.99) promises to live up to the image quality of which the Alpha 7 and 7R($629.99 at Amazon) are capable, but its asking price is comparatively high.

The lens is on the large size compared to similar kit zoom for APS-C SLRs, but is pretty light. It measures 3.3 by 2.9 inches (HD) and weighs 10.4 ounces. Despite being a little on the large size, it balances well with the A7 and A7R, even without the addition of a vertical shooting grip. A reversible petal lens hood is included and 55mm filters are supported. It does extend a bit when zooming, but only by about a half inch at the longest and shortest focal lengths (the lens is physically smallest when set to around 50mm). The front element never rotates, so using a polarizing filter is feasible. The close focus distance is 11.8 inches, which is perfectly acceptable for a lens of this type, but its 0.19x magnification capability will have you looking elsewhere for macro work.

I used Imatest to check and see just how sharp the lens is when paired with the Alpha 7. At 28mm f/3.5 it scores 2,125 lines per picture height on a center-weighted test, better than the 1,800 lines we require to call an image sharp. The extreme edges of the frame are a little murky, notching just 1,270 lines. Stopping down to f/5.6 doesn't do much to improve the center-weighted average (2,179 lines), but edges improve to 1,578 lines. At f/8 the lens is sharp from edge to edge, scoring 2,705 across the frame with edges that top 2,150 lines. Performance on the 7R is similar at f/3.5, but at f/5.6 the lens manages 2,422 lines with edges that top 1,700 lines, and at f/8 it improves to 3,492 lines with edges that top 2,400 lines.

Zooming to 35mm doesn't do much to change performance, at f/4 the lens scores 2,205 lines on the A7, and increases to 2,700 lines by f/8, with edge performance nearing 1,800 lines at f/5.6. On the A7R it's a bit sharper all around; 2,458 lines at f/3.5, and around 3,000 lines at f/5.6 and f/8, excellent edge performance at both of those settings.

The aperture narrows to f/4.5 by the time the lens gets to the 50mm setting. Center-weighted sharpness is impressive, with the lens hitting 2,385 lines on the A7 and 2,770 lines on the A7R. Edge performance is the issue here again; at f/4.5 and f/5.6 edges hover around 1,600 lines on both cameras, but at f/8 they top 2,000 lines with ease. At 70mm there's no issues with center-weighted sharpness at either f/5.6 or f/8, but edges of the frame only reach 1,400 lines at f/8 on either camera.

If you're shooting JPG, distortion isn't an issue—both the Alpha 7 and 7R correct for it automatically. But if you work in Raw, you'll have to deal with very heavy distortion at 28mm and 70mm. At the widest angle the lens shows 3.2 percent barrel distortion, which causes straight lines to curve outward. Distortion isn't evident at 35mm, but at 50mm there's 3.6 percent pincushion distortion, which increases to 4.2 percent at 70mm. This causes straight lines to curve inward. It's something that you can correct for in editing software like Lightroom, but with a zoom lens that can be a bit tricky as different focal lengths require different levels of correction.

The Sony FE 28-70mm F3.5-5.6 OSS isn't a standout lens, but it's an acceptable starter zoom. It makes some sacrifices in optical quality in order to keep its weight, and cost, at a reasonable level. The distortion it exhibits is correctible with software (and not an issue if you shoot in JPG), and the weak edge performance can be addressed via careful framing or by shooting at a narrow aperture. If you demand a better zoom lens, waiting for the Zeiss 24-70mm F4 ZA OSS that is slated for a February release is a safe bet—but save your pennies, as it's priced at $1,200.

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