That means that currently, Tamron and Zeiss are the only sources for after-market AF lenses for the Sony FE mount (and Zeiss has a long-term relationship with Sony). The reason this is significant is that lens development isn’t a trivial matter, and Tamron’s entry into the Sony market signifies the platform is mature enough to have a market of customers looking for a quality yet lower-priced version of lenses from Sony or its partner Zeiss. It’s also interesting to see Tamron taking the leadership position, and it reflects upon the company’s goals of releasing higher-end pro lenses in addition to its well-known enthusiast lenses.
Tamron designed the 28-75mm lens from the start to work with Sony’s platform, and its stated goals were to create a lens with silent autofocus, excellent optical quality and compact size. At under 5 inches long and 19.4 ounces, the lens is both smaller and lighter than Sony’s 24-70mm G Master, and at $800 to the Sony G Master’s $2,200, it’s also one-third the price.
Internally, the lens has 15 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 RXD, which oddly stands for Rapid eXtra-silent stepping Drive. This autofocus system is designed to eliminate noise and perform quickly in all AF modes.
As of press time, the lens had a software issue that prevents it from functioning properly when shooting video. A firmware update is promised and will have been released by the time you read this.
I coupled the Tamron lens to the Sony a7R III and the Sony a7 III, both of which have the most modern focusing systems in the FE mount. The body of the Tamron lens is plastic, as opposed to the metal housing found on many pro lenses, but that’s partially responsible for the lower weight of the lens relative to the Sony G Master version. I can’t speak to long-term durability of this lens versus a similar metal-bodied version, but certainly, I’d avoid situations where blows to the lens might occur. That said, the lens has some weather resistance, so I wouldn’t hesitate to take it on an adventure sports shoot, either.
Thanks to the fast “RXD” AF motor, the lens is more than capable at finding a subject and tracking a subject. In similar tests with the Tamron lens and Sony’s own lenses, it did seem that the Tamron wasn’t quite as fast at finding eyes or faces as the Sony lens, though that said, it did lock onto subjects extremely well. Sony’s glass can pick out an eyeball in even a complex scene, but the Tamron lens seems much less able to do so.
Generally, an ƒ/2.8 lens makes for a serviceable portrait lens, though the background defocus on most f/2.8 zooms isn’t as notable as on an ƒ/1.4 or f/1.8 prime, though I found the background blur on the Tamron 28-75mm to be extremely pleasing, soft and vibrant.
On a number of occasions, with indirect shade or backlighting, I found that images were slightly low contrast, something that was easy to fix in post but wouldn’t have been as likely with a prime portrait lens.
The Tamron 28-75mm is very sharp in the center of the lens, and the sharpness decreases toward the edges. That’s not atypical in a zoom lens, and not atypical at all in a budget-minded pro zoom, but is something to consider when using the lens. At the widest setting, there’s noticeable barrel distortion, something you don’t find in the $2,200 Sony G Master but less apparent midway through the zoom range. (Again, though, the Tamron lens is $1,400 less than the Sony G Master.)
Excellent image quality for the price, great background defocus, small size and excellent price—Tamron has really hit this one out of the park. At $800, the Tamron 28-75mm F/2.8 Di III RXD would make a perfect lens for the enthusiast. It’s also a great choice for the pro looking to flesh out their lineup. I could see this lens being used by a second shooter at a wedding, as a pro’s lightweight travel all-arounder or as a second-body lens where a shooter is using a more expensive prime lens or a wider zoom as their primary glass. If nothing else, this lens opens up the world of possibility for Sony’s full-frame mirrorless shooters.