Sigma 20mm F2 DG | Contemporary

Reviewers find the centre sharp at f/2 and the whole frame sharp by f/5.6–f/8, but corners wide open and overall contrast trail Sony's FE 20mm f/1.8 G. Uncorrected barrel distortion is strong, so the correction profile crops noticeably, and vignetting at f/2 is clear until about f/4.

AF is quick and practically silent for video, though single-shot focus can show a small wobble. Flare resistance is good and nine blades give crisp sunstars. The non-declickable aperture ring and mount-only sealing are the main handling criticisms.

Owners value the size, the metal construction and the tactile aperture ring, and many pair it with other I-series primes as a compact kit. It is often bought as a cheaper and smaller alternative to the Sony 20mm G.

The common complaints are the heavy distortion that needs correcting, cat's-eye bokeh in the corners, and the lack of a declick option for video.