Guys,

Just noticed something today when using my Sony DSR-390. I was zooming into an object on a white wall and during the zoom the outside edges of the image started to get darker as the zoom progressed. It also happens on my vx2000 so I figured it's a normal side effect of a zoom lens. Is this the case?

John.

Yep, it's normal.
It's called tunneling, or keyholing, depending on who you ask.
Use the search feature at the top right of the screen with one of those two keywords, and you will find several threads talking about this effect.