Conclusion

There aren't too many ultra-wide-angle zoom lenses available for Sony's range of APS-C mirrorless cameras, so it's great to see Tamron providing an option in the shape of the excellent 11-20mm F2.8 Di III-A RXD.

It does suffer from a few image quality issues - most notably obvious distortion at both ends of the zoom range and flare when including a strong light source in the frame.

Sharpness is excellent in the centre of the frame throughout all of the focal lengths, even when shooting wide-open at the fastest f/2.8 maximum aperture. It does drop off a little at the edges, though, requiring you to stop down to f/4 to achieve a similar level of sharpness.

The lens is usefully weather-sealed, another indication of its serious credentials, although unlike the very similar 17-70mm optic, there is no inclusion of Tamron's Vibration Compensation image stabilization system on this lens.

We were also disappointed by the complete lack of any physical controls on this lens - having to delve into the complex Sony menu system every time you want to change the focus mode proved to be somewhat annoying.

On a more positive note, auto-focusing proved to be quick, reliable and quiet, in both good and bad light - it was so reliable that we never had cause for complaint.

Compared to its only real main rival, the similarly priced Sony E 10-18mm F4 OSS, the Tamron 11-20mm for Sony is over 100g heavier, a couple of cms longer and doesn't have optical stabilization, but you do crucially get the faster maximum aperture, better build quality and weather-sealing, which for us gives it the edge.

If you're in the market for an ultra wide angle zoom lens with a fast maximum aperture, then the new Tamron 11-20mm F2.8 Di III-A RXD lens should definitely be on your shopping list.

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