The Tamron 70-180mm f2.8 Di III VXD (model A056) is a telephoto zoom designed for Sony’s Alpha mirrorless cameras and corrected for full-frame sensors. Announced in April 2020, it complements Tamron’s other zoom lenses for E-mount with a fast f2.8 focal ratio: the 17-28mm f2.8 Di III RXD and the 28-75mm f2.8 Di III RXD.
Physically, the 70-180mm f2.8 Di III shares the same small 67mm filter thread with the shorter zooms and it is only 81mm (3.2in.) diameter wide and 149mm (5.9in.) long – but extends when zoomed to 180mm focal length. It weighs only 810g (29 oz.) and can go down to a maximum magnification of 1:2 with manual focus at 70mm focal length. Interestingly the lens has no optical stabilization but relies solely on the image stabilization provided by the Sony Alpha mirrorless cameras.
The Tamron 70-180mm f2.8 Di III is listed at 1499 EUR (incl. 19% VAT) / 1199 USD / 1349 GBP and should become available in mid May. Ahead of my full review I’ve compared the new lens to the Sony FE 70-200mm f2.8 G Master OSS based on the information so far available from Tamron. PS – if you’re interested in the other two f2.8 zooms for E-mount in Tamron’s line-up check out my in-depth reviews: Tamron 17-28mm f2.8 Di III review, Tamron 28-75mm f2.8 Di III review. Or have a look at my Sony FE 70-200mm f2.8 G Master OSS review-so-far with lots of sample images.
Facts from the catalog
Let’s compare the Tamron 70-180mm f2.8 Di III to the Sony FE 70-200mm f2.8 G Master (“Sony” for short). As usual I’ve rated the features with a [+] (or [++]), when it’s better than average or even state of the art, a  if it’s standard or just average, and [-] if there’s a disadvantage.
Size (diameter x length): At 81 x 149mm (3.2 x 5.9in.) without lens hood the new Tamron is much smaller than the Sony at 88 x 200mm (3.5 x 7.9in). But zooming the Tamron to 180mm focal length extends the lens while the Sony does not change its length during zooming. [+]
Weight: 810g (29 oz.) without tripod foot or lens hood. That’s only 55% of Sony’s 1480g (52oz.). [+]
Optics: The Tamron 70-180mm f2.8 Di III has 19 elements in 14 groups including 6 special dispersion elements and 3 aspherical elements. This is a slightly simpler design than the Sony with 23 elements in 18 groups. Both lenses have fluorine-coating on the front element to repel water, dust, and dirt and make cleaning easier. [+]
Closest focus distance is 0.27m (0.9ft.) at 70mm focal length and 0.85m (2.8ft.) at 180mm focal length. A very good maximum magnification of 1:2 is achieved at 70mm focal length. At 180mm focal length maximum magnification is still a very useful 1:4.6 which should result in a working distance of around 0.65m. The Sony achieves a maximum magnification of 1:4 at 0.96m minimum object distance. [+]
Filter-thread: 67mm, the Sony takes 77mm filters. [+]
Image stabilization: The Tamron doe not offer optical stabilization. The lens solely relies on the body based image stabilization of the Sony Alpha mirrorless cameras. The Sony zoom lens has optical image stabilization built in which works together with the body-based image stabilization of a Sony Alpha body. 
Auto focus: Yes with built-in AF drive. Manual-focus override is by simply turning the dedicated focus ring. The focus ring probably has a variable gearing (like Tamron’s shorter f2.8 zooms for E-mount) which allows for very precise manual focus when turned slowly but cannot be switched to linear gearing. Which makes smooth focus pulling for videographers almost impossible. [+]
Covers full frame/FX or smaller. Same with the Sony. [+]
Price: 1499 EUR (incl. 19% VAT) / 1349 GBP / 1199 USD. This looks like a pretty high price for a lens without optical stabilization and only 180mm maximum focal length. But the Sony goes for 2700 EUR / 2150 GBP / 2600 USD. 
The Tamron comes without a pouch but the lens hood is included and reversible for transport. The Sony has a much nicer padded lens case. 
Aperture ring and other control elements: The Tamron has no aperture ring but offers a zoom-lock to prevent the zoom from extending when in the 70mm position. The Sony also has no aperture ring but offers a focus hold button, a focus limiter switch (full/3m) plus switches to control image stabilization and AF/MF. 
Sealing: yes, a rubber grommet at the lens-mount plus further special weather-sealing throughout the construction, just like the Sony. [+]
The score in the “features-department” is 0[-]/4/8[+] which makes the new Tamron 70-180mm f2.8 Di III look like a well rounded design. Its prominent features are its small size and weight plus the maximum magnification of 1:2.
Three Tamron f2.8 zoom lenses for E-mount
Let’s see what the MTF charts tell us about the expected performance of the new lens.
Above: Tamron 70-180mm f2.8 Di III at 70mm f2.8 (left), 180mm f2.8 (right)
Above: Sony 70-200mm f2.8 GM at 70mm f2.8 (left), 200mm f2.8 (right)
From the charts the new Tamron 70-180mm f2.8 Di III should show better resolution than the Sony FE 70-200mm f2.8 G Master at the short end. At the long end the new Tamron also shows very good resolution – but only in the sagittal direction. The meridional contrast drops faster towards the corners due to astigmatism – but with resolution still at a level similar to the Sony. All-in-all this looks very promising for Tamron’s new 70-180mm f2.8 Di III and I’m looking forward to how the lens compares in real life.
That’s it for now, but check back for my full review of Tamron’s 70-180mm f2.8 Di III when the lens becomes available!Check prices on the Tamron 70-180mm f2.8 Di III VXD at B&H, Adorama or WEX. Alternatively get yourself a copy of my In Camera book or treat me to a coffee! Thanks!