Compared @ 14mm: Swing and Tilt, Optical Decentering — two Sony FE 12-24mm f/2.8 GM and Sigma FE 14-24mm f/2.8 DG DN Art
See my Sony mirrorless wishlist.
This is an outstanding comparison for high-res digital photographers to understand the challenges of getting a good lens sample on a camera with minimal swing and tilt. It might be discourage and encourage, depending on expectations—getting view camera quality in a compact camera is pretty neat stuff even if the practical limits to build quality tolerances lead to all sorts of flaws showing up.
The Sony FE 12-24mm f/2.8 GM has a complex behavior as do all other zooms of its kind, such as the Sigma FE 14-24mm f/2.8 DG DN Art, the two behaving very similarly. I would summarize both optical designs as “outrageously good”. However, real lenses on real cameras show multiple faults that call out the computed (not measured) MTF as fantasy MTF. And that’s on top of any lens mount / sensor parallelism of the camera itself.
Includes images from f/2.8 through f/8 at up to full camera resolution, plus crops and detailed analysis.