Sigma 20mm F2 DG | Contemporary (L-Mount)

Reviewers find the centre sharp at f/2, and the whole frame sharp by f/5.6 to f/8. One lab test rated corner sharpness excellent even wide open, while another found the corners softer and darker at f/2 than Sony's 20mm f/1.8 G, which has a flatter field. Colour fringing is negligible, but uncorrected barrel distortion is strong and the correction profile crops the frame. Vignetting is clear wide open and fades by about f/4 to f/5.6.

AF is fast and nearly silent, and the lens is pleasant to handle thanks to its metal build and tactile aperture ring. Bokeh is smooth for a 20mm, though highlights turn cat's-eye toward the corners wide open. The main criticisms are the aperture ring that cannot be de-clicked, some focus breathing, and sealing that one review describes as mount-only.