A wide-angle, yes, but which one? (Part 1)

These lenses are used to shoot landscapes, panoramic images, and architectural subjects (again, for this last, with resulting straight line deformation). We tested a Tokina very wide-angle lens on Nikon and Canon mounts - the Tokina AT-X 12-24 AF PRO DX Nikon and the Tokina AT-X 12-24 AF PRO DX Canon.Since their appearance in 2004, these lenses have been joined by some serious competitors: the Canon EF 16-35mm f/2.8L II USM (2007), the Sigma 12-24mm F4.5-5.6 EX DG HSM II Canon (2011), the Nikon AF-S Nikkor 16-35mm f/4G ED VR (2010), and the Sigma 12-24mm f4.5-5.6 EX DG