In the Senior Primary Class the other day, we were talking about green screen photography, and how the illusion of adventure, danger and destruction is created in TV and films. (Check back to this post about the Evian Babies.)
Here's a video from Stargate Studios, showing how they use green screens. You may want to stop the video to check out the different scenes - the overlay with final footage and green screen filming is very quick.
Stargate Studios 2010 Virtual Backlot Demo from Stargate Studios on Vimeo.
Stargate's Vimeo channel is here, if you'd like to see their other 67 videos, and their web page is here. Some of the scenes in their videos are gruesome. I guess it's good that they're there, so that you can learn how almost everything you see on TV and in films is not real!