3 aspherical, 5 low dispersion, 1 extra low dispersion
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Tamron has managed to reinvent the popular 70-200 f2.8 with a smaller, lighter, and yet high performing lens in the Tamron 70-180mm F2.8 VXD for Sony full frame mirrorless. It is very sharp from F2.8 on. [...] It has incredibly fast, accurate autofocus [...] The lens isn’t as feature rich as competitors, but it delivers on the most important elements of focus and optical performance.
Sony Alpha Blog
[Test on 61 Mp camera] It delivers similar performances to the Sony FE 70-200 F2.8 GM in most cases and even surpass it sometimes (corner sharpness and sharpness at 180mm, portability) at half of its price. A superb Performance!