Posted 30 May 05glemon,
The brightness control may only be available with the pro version with a few other filters. It is rather strangely in in the file / export menu, command e
Choose "Movie to QuickTime Movie" from the Export pop-up menu.
Click Options, click Filter, and select the filter and settings you want to use.
You will find Brightness and Contrast there. I am not sure if any of these are in the non pro version but you can probably do them in iMovie.