You may not have considered just what you can do with Live View, because the capability is so novel. But once you’ve played with it, you’ll discover dozens of applications for this capability, as well as a few things that you can’t do. Here’s a list of Live View Do’s/Don’ts/Cans/Can’ts.
Preview your images on a TV. Connect your EOS 40D to a television using the video cable, and you can preview your image on a large screen.
Preview remotely. Extend the cable between the camera and TV screen, and you can preview your images some distance away from the camera.
Shoot from your computer. Canon gives you the software you need to control your camera from your computer, so you can preview images and take pictures ...