Tamron 20mm f/2.8 Di III OSD M1:2 - Lab Test / Review
Lens Reviews - Sony Alpha (Full Format)
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Review by Klaus Schroiff, published August 2021


In our last part of our Tamron prime lens review mini-series, we'll have a look at the Tamron 20mm f/2.8 Di III OSD M1:2 - probably the most interesting of the triple. It sits outside the coverage of standard zoom lenses and for photographers on a budget it can be a first step into the true ultra-wide segment. This doesn't mean that there is much of a physical difference compared to its more moderate cousins (24mm f/2.8 and 35mm f/2.8). As mentioned already in the previous review, you'll be hard-pressed to distinguish between them. However, this certainly helps in keeping manufacturing costs at bay. Ultra-wide lenses tend to be more expensive but Tamron managed to keep the price tag around a very moderate 300 USD/EUR - which is commendable especially for a full format lens.

For this amount of money, you can't expect professional-grade quality. The chassis is made of average quality plastics based on a metal mount. The rubberized focus ring operates smoothly but there is a cheap feel to it. Surprisingly, the lens has some seals making it moisture resistant albeit there isn't a word about dust protection. While the length of the lens doesn't change during focusing, there's a moving inner lens tube. It isn't fully clear why Tamron designed the lens to be relatively long because this tube is quite deeply recessed by about 1.5cm. A petal-shaped lens hood is provided.

The AF system uses a linear extension system. Typical for this focusing type, the AF speed is on the slow side but it's at least noiseless. The same can't be said about the aperture mechanism. When stopped down, you can hear that the camera is opening/closing the aperture during focusing operations. Once again, this has a cheap feel to it. As usual, manual focusing works "by-wire". The precision is pretty good in this case. A specialty of the lens is its close-focusing capability. It can focus down to a max object magnification of 1:2 (hence the M1:2 in the lens name). An image stabilizer has not been implemented which is hardly surprising given the price point.

Optical construction9 elements in 8 groups inc. 1x aspherical and 3x LD elements
Number of aperture blades7 (rounded)
min. focus distance0.11m (max. magnification 1:2)
Filter size67mm
Hoodbarrel-shaped with frame window (bayonet mount, supplied)
Other featuresdust & moisture resistant
MountSony FE

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