2 advanced aspherical, 1 extra low dispersion aspherical
A lens stretching from an ultra-wide 20mm through to a short telephoto 70mm, focusing right down to almost half-life-size, is an amazing and versatile option for Sony A series users [...] The f/4 aperture is no real obstacle in these days of high ISO cameras [...] Highly versatile and Highly Recommended.
It is one of the more exciting lenses released in recent years. [...] In RAW images, the barrel distortions are nothing short of excessive at 20mm [...] even so, the quality remains almost surprisingly high. [...] Lateral CAs are also quite low. [...] A single major weakness that is image-affecting from an end-user perspective, it's the bokeh. [...] The lens is pretty resistant to flare effects.
Leaving aside, for the moment, the price, it’s clear that the Sony FE 20-70mm F4 G is a fine optic that delivers sharp, detailed images even when paired up with Sony’s high-resolution full-frame bodies [..] It’s a lens I really enjoyed using, with its extended wideangle range and impressive close-up capability.
From time to time you see such unique lenses being launched as the Sony FE 20-70 mm f/4 G, tested here. My joy is not spoiled by the fact that they are very hard to assess because if you deal with a unique instrument you have no reference point and almost no rivals to compare it with.