It is not vignetting that you're describing, it's light fall off. Vignetting happens when something obstructs the light entering the lens, such as a lens hood that's too small.
Shel "You meet the nicest people with a Pentax" > [Original Message] > From: Jostein < > Interesting that they address vignetting with wide-angles. > Vignetting wide-angles has always been Canon's weak side, iirc.
