Use the Aged Film video effect to make your video clips look like they were filmed a long time ago and are playing on a shaky projector.
iMovie Video Effects - Adjust Colors
Effect In, Effect Out:To apply the effect to only part of the video clip, move the sliders to the places/times when you want the effect to begin and end. Leave them both set to 0:00 to apply the effect to the entire clip.
Exposure: Increase or decrease the exposure, or brightness, of the video clip with this slider bar.
Jitter: Use this slider to make the clip more or less jittery on the screen.
Scratches: Here you can increase or decrease the number of scratches and artifacts (such as dust) added to your video clip.