Viltrox's budget full-frame ultra-wide — 20mm f/2.8 with AF for multiple mirrorless mounts.
The Viltrox AF 20mm f/2.8 is a compact autofocus ultra-wide prime for full-frame mirrorless, available for multiple mount systems. It provides 20mm coverage at f/2.8 with AF at a fraction of first-party pricing.
Optically adequate — sharp from f/5.6 with acceptable centre performance at f/2.8. Stepping motor AF is quiet. Some edge softness and distortion typical of budget ultra-wides. Full-frame coverage. USB-C for firmware updates.
Multiple mount versions. Compact and lightweight. No weather sealing. 52mm filter thread — accepts standard filters at 20mm. De-clickable aperture ring. Minimum focus distance approximately 20cm.
Available used very cheaply. The Sony 20mm f/1.8 G and Nikon Z 20mm f/1.8 S are dramatically better but much more expensive. For budget ultra-wide needs where price is the primary concern. Check for firmware updates via USB-C.