This is a useful technique if you want to make an object into an animation using several still shots from a camera/digital camera. Once you have each individual picture taken, you can then edit the background out on each frame, and place your own, static background into each frame which will make the object appear rotate.
Depending on what frame rate you want will determine how many frames/pictures you would need to achive the desired results. Full motion video NTSC is 29.97 FPS (Frames per second)... you can honestly get away with as little as 15 FPS, but I wouldn't go any lower than that.
Now, with that said, let's see some live motion with your camera's..