As part of Sony's top-tier G Master lens series, the FE 24-70mm F2.8 GM ($2,199.99) carries with it some lofty expectations. It opens up to f/2.8, regardless of focal length, is built tough and sealed against dust and moisture, and locks focus quickly. There are some optical drawbacks, notably barrel and pincushion distortion at different focal lengths, but that's not atypical, even for a top-end zoom lens of this type. It's a stronger performer than the FE 24-70mm F4 ZA OSS ($898.00 at Amazon) , but comes at a higher price and omits in-lens stabilization. That's not a big deal for photographers who have moved to the latest generation of Sony mirrorless cameras, which include in-body stabilization.

Design

The FE 24-70mm ($2,198.00 at Amazon) is a typical size for a lens of its type, measuring 5.4 by 3.5 inches (HD) and weighing in at just under 2 pounds. It balances well on a full-frame body like the Alpha 7R II with which I tested the lens, but may be a bit much for an APS-C model like the Alpha 6000. The front element supports 82mm filters.

The 24-70mm range has long been the standard for working professionals and enthusiast photographers alike. It's wide enough for use in tight spaces and landscape work, and zooms to cover short telephoto distances. It's most often paired with a telezoom, like the superb FE 70-200mm F2.8 GM OSS ($2,598.00 at Amazon) .

The lens is finished in black, with a polycarbonate barrel, internal weather sealing, and rubberized focus and zoom rings. It has a telescoping design, so it does extend when zoomed. It can be locked at 24mm, so the barrel won't creep out when it's hanging at your side. The zoom ring has set marks for capturing photos at 24, 35, 50, and 70mm. A reversible lens hood is included.

There's a single button on the lens. It pauses the autofocus system so you can lock in focus, regardless of the focus mode set on the camera. There's also a toggle switch to change between manual and autofocus.

The 24-70mm focuses as close as 15 inches, measured from the image sensor, so you can get pretty close to subjects. It's a solid working distance, delivering 1:4.2 macro magnification at 70mm.

You don't typically get image stabilization with a 24-70mm f/2.8 lens—the AF-S Nikkor 24-70mm f/2.8E ED VR ($1,896.95 at Amazon) is an exception to the rule. The Alpha 7 II ($898.00 at Amazon) family includes in-body 5-axis stabilization, so owners of newer cameras won't notice the lack of in-lens stabilization.

Image Quality

I tested the 24-70mm F2.8 GM with a 42MP Alpha 7R II. It's currently the highest resolution Sony camera available, but the company says the G Master lenses are designed with future, higher resolution sensors in mind.

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At 24mm f/2.8 the lens scores 2,514 lines per picture height on a center-weighted Imatest evaluation. That's better than the 2,200 lines we want to see from a lens paired with a high-resolution camera. The center third of the frame is tack sharp (3,559 lines), but there is some softness as you move away (1,761 lines) and at the periphery (1,607 lines). Still, it's stronger at the edges than the 24-70mm F4 OSS is at f/4, which has edges that show just 1,068 lines.

The lens enjoys a significant improvement in resolution at f/4. It scores 3,519 lines on average, with edges that are crisp at 2,844 lines. The trend continues at f/56, where it improves to 3,963 lines with edges that are excellent (3,549 lines). Landscape shooters will enjoy peak performance at f/8 (4,188 lines), a setting at which the lens delivers results that are superb from center to edge. There's a mild drop in resolution at f/11 (4,133 lines), and diffraction cuts into resolution at f/16 (3,657 lines) and f/22 (2,658 lines).

Results aren't that far off at 35mm. The average score at f/2.8 is 2,598 lines, and edges show 1,738 lines. At f/4 the score jumps significantly (3,870 lines) and edges are nearly as sharp as the average (3,309 lines). The sweet spot starts at f/5.6 (4,227 lines) and continues at f/8 (4,225 lines) and f/11 (4,124 lines). Resolution drops at f/16 (3,968 lines) and f/22 (2,692 lines).

At 50mm the image quality at f/2.8 is much better—3,569 lines, with edges that approach 3,000 lines. Resolution improves at f/4 (3,717 lines), f/5.6 (3,776 lines), f/8 (4,005 lines), and f/11 (4,111 lines), before dropping off at f/16 (3,746 lines) and f/22 (2,843 lines).

Expect similar performance at 70mm. The lens shows 3,249 lines at f/2.8, with sharp edges (2,229 lines), and the score creeps upward at f/4 (3,537 lines), f/5.6 (3,538 lines), f/8 (3,697 lines), and f/11 (3,918 lines). There's a slight drop at f/16 (3,758 lines), and a more notable one at f/22 (2,824 lines).

The lens does show some distortion throughout its zoom range. At 24mm there is 3.3 percent barrel distortion, which makes straight lines appear to have a noticeable outward curve, like the hoops of a barrel. There's no noticeable distortion at 35mm, but you do get 1.8 percent pincushion distortion at 50mm and 70mm. This gives the same straight lines an inwardly curved appearance. Thankfully modern image editing software makes short work of distortion. You can remove it with a single click in Lightroom ($9.99/Month at Adobe) .

Lightroom also evens out illumination through the frame. At 24mm f/2.8 the corners of the frame lag behind the center by about 2 f-stops (-2EV). The deficit is cut to -1.5EV at f/4 and f/5.6, and about -1EV at f/8 and narrower.

At 35mm and 50mm the corners lag behind the center by less than a stop, even at f/2.8, which is negligible in the field. You will have to deal with some dimness at 70mm, about -1.4EV at f/2.8 and -1.2EV at f/4, but at narrower apertures the deficit is once again negligible.

Conclusions

The FE 24-70mm F2.8 GM is the zoom lens that serious photographers were clamoring for when Sony first launched its full-fame mirrorless system. An f/2.8 standard zoom is a must-have lens for anyone covering events. It took a few years, but now it's here, and designed for high-resolution cameras of the present and future.

There are some optical compromises inherent in designing a zoom lens, but the major sins of the FE 24-70mm F2.8 GM—distortion at the extreme ends of the zoom range and dim corners—are easily remedied with software. The edge softness at f/2.8 in the 24 to 35mm range cannot, which is why we're not naming the lens as an Editors' Choice. In many instances a shallow depth of field will hide the edges when shooting wide open, but photographers should take care to stop down to f/4 or narrower if image quality at edges of the frame is crucial to a shot.

Sony mirrorless system owners have some options when it comes to a standard zoom. Canon and Nikon SLR lenses can be used, with full autofocus, when paired with an adapter. Sticking with native lenses, the FE 24-70mm F4 ZA OSS is a solid alternative if you don't mind a narrower aperture, and at half the price it's hard to argue against in terms of value for your dollar. I'm less enthusiastic about the FE 28-70mm F3.5-5.6 OSS ($398.00 at Amazon) , as it doesn't offer as much wide-angle coverage.

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