I jump a cx105 with a Opteka .43 and have a similar issue. Fully zoomed out, I get vignetting, but only when I transfer the footage to a PC. It doesn't vignette on a flat screen TV or rear projection TV. I have a couple of friends who jump the same setup and have no vignetting issues at all. I'm not sure whether it would have anything to do with the step up ring? That's all I can think of that may be different. Maybe my step up ring secures the lens further/closer to the camera lens? I'm not sure if this would have any effect? When I've jumped the .43 or the .3 I've zoomed in a tiny bit to be on the safe side!
