The-Digital-Picture has completed their review of the Sigma 12-24mm f/4L DG HSM Art.
Image Quality
From the always-important image sharpness perspective, this lens is a very good performer with a caveat that I will of course explain. At f/4, this lens is quite sharp in the center of the frame over the full focal length range aside from performance becoming modestly softer from 20mm through 24mm. Stopping down to f/5.6 brings sharp center of the frame results to the entire focal length range……….
……… I mentioned the caveat. What I didn't notice during this shoot was focus shift. As this lens is stopped down, the plane of sharp focus shifts farther away. Because Canon cameras focus with a wide open aperture, this change is not accounted for during either viewfinder or Live View-based focusing (AF or MF). Stopped down manual focusing in Live View will account for the change, but … this is not how we typically focus. Read the full review
It looks like Sigma has another winner on their hands with the 12-24mm f/4 DG HSM Art series lens, especially when you factor in the fact it costs about $1000 less than the Canon EF 11-24mm f/4L.
Sigma 12-24mm f/4 Art $1599: B&H Photo | Amazon | Adorama | Midwest Photo