Effect: Blue Screen

Description
Performs a blue screen compositing operation. Areas of the image which are blue are considered to be transparent. NOTE: this effect is faster than the "Smooth" version, but may produce lower quality results for some scenes.

Controls

Outside Fill:		Determines the extent to which the background (blue) region of the image spreads into the foreground region.
Inside Fill:		Determines the opacity of the foreground (not blue) region of the image.
Choke:		Shrinks the edges of a mask and makes those edges harder.

Notes
To use this effect, place TWO clips of the SAME EXACT LENGTH in the timeline, next to each other. Select the first clip and apply the effect.

NOTE: In previewing, a few frames at the beginning and end of the clip may appear incorrect. This is due to a known bug in iMovie 2. However, the final result using an Apply will be correct in all cases.

Examples

Source	Background	Result