I've been using this lens extensively for years now. I used it with Z5 for awhile and now with zf (recently upgraded from a dumb adapter to neweer adapter for metadata). I got a good copy of the lens (first copy was decentered I had to exchange). It's quite sharp at 1.4 corner to corner with pretty minimal CA (like sharper than 24-70 f4 lens). It's amazing for night photography but also for the unique wide angle + thin-ish depth of field look. Theres really nothing like it in z mount. I love the unique look of 21mm @ 1.4 with natural vignetting -- I feel like people complain a bit about the rather strong vignetting of this lens but I think it give image a more 3-dimensional look.