I know there are enough lens nerds here that enjoy these MTF tests. Roger and his staff do a good job of it. Find them HERE. A few comments from his finding: On the FE1635Z/4: "Overall, both from an MTF and a copy-to-copy variation standpoint, the Sony FE lens is as good as, and sometimes better than, the Canon and Nikon offerings." "The Sony FE 16-35mm f/4 actually is excellent for an ultra-wide zoom, and again, it seems to have decent sample variation." On the FE2470Z/4: "So the bottom line is while there is definitely some copy-to-copy variation among the Sony f/4 zooms, it doesn’t really appear worse than most zoom lenses." "I will say I’m pleasantly surprised. The Sony FE 24-70mm f/4, while not a great lens is adequate (note I didn’t say adequate for the price, I said adequate) and its copy-to-copy variation isn’t bad." Summary: "Would I buy them? Probably not the 24-70 f/4 unless I had no options, but I wouldn’t hesitate on the 16-35mm f/4."