What is vignetting?
It's something they use in wine growing regions to keep the birds off the grapes.
(sorry, couldn't resist).
Easier just to show you, got this with the fuji tele on my 602.
When the edges of a picture are faded to black, caused by too many
filters on a lens or a lenshood. The lens includes part of the edge
of the said filters/lenshood in the picture. Normally seen as a
darkening in the corners of the picture when on wide angle setting.
(Usually not seen until it is impossible to retake the shot).
Therefore if any attachment (accessory lens, filter, lenshood) is
purchased for a camera be sure to check with the lens at its widest
Also a way of decorating a picture by intentionally fading out to
the background colour usually but not always white.