Verdict

Compact size, light weight, low price, and an above-average magnification of 1:2 makes the Tamron 20mm f2.8 M1:2 an interesting proposition for photographers looking for an ultra-wide lens for their full-frame Sony Alpha mirrorless camera. 20mm offers a 10 degrees wider angle of view over a 24mm lens and almost 20 degrees over a 28mm lens which might just be the ticket when shooting landscapes or architecture. Its focal ratio of f2.8 does not seem like much but is perfectly OK when you go for depth-of-field over subject isolation. More important when shooting ultra-wides is a good resistance against flare and glare as it’s often hard to avoid strong light-sources in an image. Fortunately the new Tamron is very good in this respect.

What are the weak(er) points? Personally I was most disappointed by the soft performance of the lens in close-up shooting outside the center. I simply expected more from a lens which was specifically designed to reach a maximum magnification of 1:2. Even at a magnification 1:4 the new Tamron falls way behind the Sony FE 20mm f1.8 which does not boast about its close-up performance. Then there is a very slow autofocus which might not bother you when shooting still subjects. And barrel distortions of the lens are very high but can be straightened out with the Adobe supplied lens-profile. My final point is the very short working distance of 3cm (1in.) at minimum object distance. But this is not Tamron’s fault but simply a consequence of the laws of optics: Any 20mm lens would have a very short working distance at 1:2 magnification.

To put this all in perspective let’s have a closer look at how the new lens compares to some alternatives.

Above: Sony FE 20mm f1.8 G (left), Tamron 20mm f2.8 M1:2 (right)

Compared to Sony FE 20mm f1.8 G

The Sony FE 20mm f1.8 G is a very good wide angle prime lens for owners of Sony’s Alpha mirrorless cameras: it has a nice feature set including a de-clickable aperture ring and multi-purpose focus hold button, and its optical performance surpasses the Tamron 20mm f2.8 M1:2. Plus you get 1.3 EV more light gathering power and better Bokeh over the Tamron with the f1.8 focal ratio and the Sony focuses twice as fast. Regarding close-up shots: The Sony may only go down to a maximum magnification of 1:3.8 versus the 1:2 of the Tamron but it produces sharper shots at its maximum magnification of 1:4. This gives you more leeway for cropping and also offers a better working distance. But you pay for what you get – with a slight increase in size and weight and a steep markup in price: 1100 EUR / 899 USD versus 400 EUR / 349 USD. This makes the Tamron 20mm f2.8 M1:2 a clearly better fit for a limited budget.

For more details see my Sony FE 20mm f1.8 G review where the lens earned a Highly Recommended.

Compared to Tamron 17-28mm f2.8 Di III

Optically the Tamron 17-28mm f2.8 Di III is sharp and contrasty even under adverse contra-light situations and delivers very usable close-up performance too with a maximum magnification of around 1:4.5. It may not be the sharpest lens in the full-frame corner at medium distances but it is still sharper there than Tamron’s 20mm f2.8 M1:2 and it delivers very sharp landscape and architecture shots. Its 1.6x zoom range may look somewhat limited but that still covers a very useful range of focal lengths for wide-angle shots: At 17mm it has a 10 degrees wider angle of view and at the long end it has 40% more reach than a 20mm lens. This makes the price of 850 EUR / 900 USD look well worth it.

For more details see my Tamron 17-28mm f2.8 Di III review where the lens earned a recommendation.

Tamron 20mm f2.8 M1:2 final verdict

The Tamron 20mm f2.8 offers a fairly unique proposition for owners of Sony’s full-frame mirrorless cameras. It’s a small and light prime lens with weather sealing, delivering good to very good resolution in the APS-C image-circle at normal shooting distances. It lets you shoot confidently under adverse contra-light situations which is a boon especially with the very wide angle of view and at close-up shooting.

On the downside, its unique selling point of 1:2 magnification delivered results that looked mushy outside of the centre in my tests and of course avoiding shadows at these distances is going to be hard with any ultra-wide lens. Plus the Tamron is very slow to focus, although this won’t be a big issue for mostly static subjects.

Ultimately while Sony’s FE 20mm f1.8 G out-performs it in most respects, the Tamron comes in at comfortably lower price with the benefit of closer focusing – so long as you understand its limitations. And it’s this good price performance ratio that deservedly earns the Tamron 20mm f2.8 a recommendation.

Good points:

• Very small and light.
• Low price.
• Very good maximum magnification of 1:2.
• Very high contrast and resistance against flare, glare, and ghosting.
• Good to very good resolution in the APS-C image-circle at normal shooting distances.
• Good weather sealing.

Bad points:

• Very slow to focus.
• Very short working distance at close-up shots.
• Disappointing close-up performance outside the center.
• Very high barrel distortions before correction.