Canon RF 16mm F2.8 STM

Reviewers agree the centre is sharp, but disagree on the edges. On a 45MP body one test found the borders only acceptable and the corners mushy at f/2.8, improving little on stopping down because the distortion correction stretches the outer field; on 20-30MP bodies the results were much better. Another lab test found sharpness very good over most of the frame from f/2.8 and into the corners by f/5.6, though it rated centre sharpness a little below other RF lenses.

Uncorrected files show close to 10% barrel distortion and near-black corners, so correction is effectively mandatory; with it applied, distortion and vignetting are well handled. Lateral fringing is either low or easily corrected. Autofocus is quick, with a quiet high-pitched sound. Both reviews call it outstanding value and note the lack of weather sealing and the optional hood.

Owners like how small, light and cheap it is, and many keep it in the bag as a spare ultra-wide or use it for starscapes, travel and snaps with children and pets. The 0.13m close focus gets frequent praise, and some use it on APS-C bodies as a compact everyday prime.

The common complaints are soft corners and heavy vignetting that need correction, distortion that remains visible with straight lines near the edges, the expensive optional hood and the small 43mm filter thread. Several say it does not match L or Art lenses but is more than good enough for the money.