See my Sony mirrorless wish list.
The 12mm focal length is not easy to do well. Canon’s 11-24mm f/4L is a very fine lens, but it costs a lot more and is very large and heavy. Sony has done a good job, but there is something to be desired. Still, the size and weight proposition and some stopping down are all reasonable things.
This aperture series with the Sony FE 12-24mm f/4 G at 12mm explores near-to-far performance.
It also includes a two-frame focus stack at f/1 for which distortion was corrected, and how correcting distortion affects the micro contrast, made possible by the f/9 and f/13 frames which are not corrected for distortion.
Includes images up to full resolution from f/2.8 through f/13. Also, a 2-frame focus stack that corrects distortion is included for comparison with f/9 and f/13.
The about $1699 Sony 12-24mm f/4 G with its 12-17mm range to complement the Zeiss Loxia 21mm f/2.8 makes a lot of sense. It’s a lens I’d like to have in my bag just for that 12-17mm range—I wish Sony had optimized as a 12-18mm and had forgotten about trying to do the 18-24mm range.