My webcam gives out a dark almost negative picture

Launch the logitech toolbar - make sure no video effects are selected (2 theatre masks on toolbar)
Open 'settings (2 cogs on toolbar) try and tune the picture.

If unsuccesful
Disconnect webcam
Uninstall software
Restart computer
Go to Logitech site and identify your webcam
Download software - connect webcam when prompted


http://www.logitech.com/index.cfm/405/&cl=us,en?prodcrid=405