Well, I finally took some time to take a few sample shots with my Tokina 12-24 f4 on my 1D MkI. I knew that the Tokina would not work for FF bodies especially at the 12mm end, but how much vignetting will I get with a 1.3 crop body??? Here's the answer... the 1st photo is at 20mm, the second is at 24mm.

