What does the "Camera Clip" checkbox do in the "Background Images", "Movie Clip" tab do? I have been trying to overlay graphics on a video using Blender (2.77), and part of that is setting the source movie as a background in the 3D view.  As I was setting the movie clip (and getting frustrated trying to sync the times between the timeline and the VSE), I started wondering what the "Camera Clip" checkbox does in the "Movie Clip" tab.  The tooltip says "Use Movie Clip from Active Scene Camera", but I don't know how to add a movie clip to the active scene camera except to add one as a "Background Image".



I've looked through lots of help articles and done lots of searches, but no one seems to have written a plain explanation of this checkbox.  Can anyone please provide some insight?
The Camera Clip option is referring to the active movie clip for the scene. This would normally be the clip that you are using for camera tracking.

In the scene properties you will find the setting for Active Clip. This active clip for the scene is the one referred to by the Camera Clip setting. The available clips are the clips that have been loaded into the movie clip editor for camera/object tracking.



While the same clip can be chosen in the background settings, by using the scene's active clip you can use the same setting in multiple views and change them all in one place.