Conclusion

The new Tamron 28-75mm F2.8 Di III RXD isn't the best standard zoom lens for Sony full-frame mirrorless cameras in terms of outright image quality, performance and build quality, but it is currently the best lens in terms of its cost to performance ratio, offering a lot of bang for not a lot of buck.

This is a versatile walk-around lens with a fast maximum aperture that consistently delivers great images with lovely bokeh when shooting wide open. In the centre of the image it's bitingly sharp throughout most of the zoom and aperture range, only falling off a little at 75mm. Performance isn't as good at the edges of the frame, though, requiring you to stop down to f/5.6-f/8 to get the best sharpness.

The 28-75mm F2.8 Di III RXD produces very nice bokeh effects thanks to the 9-blade iris diaphragm, although there's some obvious vignetting and barrel distortion at 24mm, even when in-camera corrections are turned on. Overall, though, other than the lack of edge sharpness at f/2.8-f/4, there's not too much to complain about in the image quality department.

Build quality is good rather than excellent. It's not quite at the same level as the metal construction of Tamron's SP lenses or the better Sony zooms, but the polycarbonate construction does at least ensure that the 28-75mm F2.8 Di III RXD is very light. 

The new auto-focusing system proved to be reliably quick and accurate on the Sony A7 III that we tested the lens with, for both still and moving subjects, and it's also fully compatible with all of Sony's focusing modes. This lens doesn't have a built-in optical image stabilisation system, instead relying on Sony's in-camera system, which will be fine for everyone except those who own a first generation Alpha camera (which don't have built-in OIS).

The official retail price of the Tamron 28-75mm F2.8 Di III RXD is certainly very attractive and one of the main reasons why it has garnered such attention, with pre-sales exceeding Tamron's expectations. It represents a major step-up from the cheap but not so cheerful FE 28-70mm f/3.5-5.6 OSS, and we'd argue it's also a better bet than the similarly priced FE 24-70mm f/4 ZA OSS Vario-Tessar Carl Zeiss T* lens. There are two Sony lenses that out-perform Tamron's new lens - the FE 24-105mm f/4 G OSS and the FE 24-70mm F2.8 GM - but both are a lot more expensive, with the first offering a slower maximum aperture and the second being much bigger and heavier.

In summary, there's a lot to like about the Tamron 28-75mm F2.8 Di III RXD and not a lot to loathe. If you're in the market for your first standard zoom lens (and a lot of new A7 III owners are) you should take a very serious look at the very impressive Tamron 28-75mm F2.8 Di III RXD.

Ratings (out of 5)
Design	4.5
Features	4.5
Ease-of-use	4
Image quality	4
Value for money	5