>I understand that you can't change it in Live View, but if >you set it to, let's say, f/18 in aperture view, will it shoot >video at f/18 when you go back to live view? Or will it just >go back to wide open?
It will shoot the video at f18. This is very easy to check. First use a lens where you can see the aperture blades when it's stopped down. Then set the aperture to f18 or f22. Turn on Liveview. Then turn on movie mode and start recording. If you now look into the lens you'll see the aperture is stopped down while the movie is recording.