I have read some threads in which some users of the 18-200mm VR lens are saying that they are getting some vignetting. I am guessing, but it could be because of a UV or clear filter placed over the lens. Has anyone had this experience here and if so are you using a regular sized filter. There are some slim UV filters available but at a premium price. Or a step up ring could work but that makes the lens hood unusable. I like the idea of a step up ring to use my 77mm CP filter on the 18-200 also so I will probably get one anyway. I have decided it is better to have a protective filter, so given that, does anyone have any thoughts?