With Sony’s mirrorless systems growing in popularity among outdoor photographers, where the relatively small size of the body, high-resolution sensors, image quality and features (like silent shutter) make them attractive tools, it’s natural that third-party lens makers are offering alternatives to Sony’s own optical lineup.
The newness of the system, compared to DSLR lines like Nikon and Canon, means there have been less optical choices for Sony E-mount than for more mature systems. To be fair, the Sony system originally hails from Minolta (A-mount), which Sony purchased, but it’s the mirrorless Alpha (E-mount) camera line that’s disruptive and relatively nascent.
When the Sony mirrorless cameras first arrived, the most common lament was that there were not enough native lenses. That was lessened a touch by a selection of Zeiss lenses, but it took a few years for Sony to beef up its arsenal. With a run of 27 lenses and 2 teleconverters, Sony now has a range of focal lengths from 8mm to 800mm.
It’s hard now to complain that Sony doesn’t have enough glass for its full-frame mirrorless cameras, but in Canon and Nikon’s space, third-party lens makers like Tamron, Sigma and Tokina have been producing compatible lenses, supplementing the array of optics available from the camera manufacturers. Sigma started to ship its Art lenses with the Sony mount, though these don’t perform as well on the Sony cameras as they do on their Nikon and Canon counterparts because the focusing motors used in DSLR lenses differ from those used in Sony’s mirrorless lenses.
This is a roundabout way to discuss the importance of the Tamron 28-75mm F/2.8 Di III RXD—it’s a lens designed specifically for Sony’s system. The “RXD” part at the end of the name refers to the high-speed linear motors in the lens, the kind that efficiently drive lenses for the Sony platform. By producing a Sony-specific lens, Tamron’s betting on the success and longevity of the E-mount camera line.
For all intents and purposes, the Tamron 28-75mm lens is essentially a 24-70mm lens (4-5mm isn’t that much difference), and as such should be considered as an alternative to Sony’s two 24-70mm lenses, the Vario-Tessar T* FE 24-70mm f/4 ZA OSS and the FE 24-70mm f/2.8 GM.
Tamron has set the price for its lens at $800, which is a respectable place for a lens of this focal length with a fast constant maximum aperture. For comparison, the older Sony 24-70mm f/4 has a price about $650, but its maximum aperture is a stop slower. The Sony 24-70mm f/2.8 GM lens is priced around $2,000, which makes it better suited for the pro looking for the highest-performance lens with this zoom range.
The questions are, does the Tamron provide a good enough value over the less-expensive 24-70mm f/4 and close enough performance to the 24-70mm GM to make it a bargain at $1,200 less? The answer to both questions is (a qualified) yes. A professional looking to outfit their kit with the best-performing 24-70mm in the Sony lineup should get the Sony G Master lens—it’s worth the price. But Tamron isn’t aiming to be the top-tier lens in this space; it’s looking to create a great value in a lens that could be the primary one for an enthusiast or the backup lens for a pro or second shooter.
The Tamron lens is particularly compact for a 24-70mm, at just over five inches long and weighing under 20 ounces. Putting the lens on a camera makes it feel particularly transportable. This is a lens I’d easily take with me on a trip somewhere instead of the G Master lens. Inside are 15 lens elements in 12 groups, with an XLD (extra low dispersion) element, a glass aspherical element, two hybrid aspherical elements, an LD (low dispersion) element and Tamron’s aforementioned RXD motor, which stands for Rapid eXtra-silent stepping Drive.
The body is made of plastic instead of metal, though I’m not sure how this would affect durability in the long run. A metal body will be more ding resistant, but the plastic body doesn’t protrude as far as the other lenses in this class, so it is less likely to hit things.
The lens doesn’t focus quite as adroitly as the Sony 24-70 f/2.8 GM (we did not have the 24-70mm F4 on hand to compare), and that’s to be expected. Sony’s internal processors know precisely how to control their own branded lenses, and third-party lenses typically focus just below the speed of native glass. The focus at the edges isn’t as fast as a native Sony lens, and it felt like the eye-detect focus was less successful, though it’s hard to test that side-by-side. The lens was more than fast enough to focus on moving people, animals and vehicles. In my typical AF testing environment, I sent several kids out on bikes to ride around me, and the lens nailed most of the shots.
To get the most out of the lens, I tested it with the Sony a7R III to see how it resolved on a 42-megapixel sensor, and the results were excellent for the price point. The lens is very sharp in the center (typical for a zoom lens) and less sharp at the edges (also typical in a zoom lens). How much less sharp at the edges depends on aperture and focal length, but generally speaking, when wide open, the lens has noticeable distortion at the corners. This is the kind of predictable distortion that apps like Lightroom and Capture One are usually able to correct for, but I always prefer having it right at capture.
In some cases I saw noticeable barrel distortion, and in some cases I did not. I’m not sure exactly what the combination is between the focal length, aperture and subject that makes this distortion, but it would be good to pay attention to the edges of the lens when shooting landscapes with discernable objects like trees or mountains at the edges.
For portraits, flora and fauna, the lens is a great choice. This lens has a nice, pleasing bokeh, and so centered (or slightly off-center) portraits shot wide open look good, and any corner sharpness or distortion issues are eliminated in the bokeh effect.
The minimum focus distance is surprisingly close. I used the Tamron lens alongside the Sigma 90mm macro at the New York Botanical Garden, and while I (naturally) couldn’t get a 1:1 ratio and couldn’t get as close as with the Sigma, I was able to take some very nice close-up images. With a 42-megapixel sensor, it’s possible to crop to a much closer 1:1 ratio and still end up with resolution equivalent to an image shot on a smaller sensor, but this only works if there’s enough clean image quality to start with that when you crop you’re not just magnifying blurry details. The Tamron lens performed surprisingly well at capturing these small details, and I’ve successfully cropped a number of flower shots, and the resolution holds up.
If you’re a Sony shooter looking for a generally great wide-to-tele zoom at an even better price, this lens is an excellent value.