The Slow Motion Smoother Effect makes your home-made slowed down clip look like a professional clip. Unlike some other iMovie plug-ins, your whole clip will be slowed down. You will not loose the end of your clip.
To slow down a clip, iMovie duplicates each frame. The visual result is as if iMovie drew the next frame after a longer period of time compared to a real-speed clip. This doesn't give a flawless playback. The Slow Motion Smoother Effect fills the gaps between two frames, making your clip playing flawless.
(Please let us know if you think we should support older versions of Mac OS and iMovie: firstname.lastname@example.org)