The Tamron 70-180mm f/2.8 Di III VXD lens is the final entry into the company's trinity of f/2.8 zoom lens, and like the 28-75mm f/2.8 and 17-28mm f/2.8, it is quite a bit cheaper than similar first party lenses. If you are wondering how it compares to the more expensive options, check out this great comparison with the Sony 70-200mm f/2.8 and 70-200mm f/4.