Canon's stabilised L-series ultra-wide — IS is rare at this focal range — with excellent edge sharpness.
The Canon EF 16-35mm f/4L IS USM (2014) was the first Canon ultra-wide zoom with optical IS — approximately 4 stops. It offers a lighter, stabilised alternative to the EF 16-35mm f/2.8L II USM.
Many reviewers consider it sharper than the f/2.8L II, particularly in the corners. Edge performance at 16mm is impressive. Ring USM provides fast, quiet AF. The f/4 aperture limits astrophotography versus f/2.8 versions.
Canon EF mount, 77mm filter thread. L-series construction with weather sealing and fluorine front coating. IS operates quietly — unusual for ultra-wides where stabilisation is uncommon. Internal focusing.
Good used availability. Check IS for smooth operation — grinding indicates bearing wear. Test corner sharpness at 16mm f/4. The RF 15-35mm f/2.8L IS is the mirrorless successor with both IS and f/2.8 but costs much more.