This tutorial will show you the basics of using the Chroma Keyer in Sony Vegas. First you'll need two video clips to work with. One with some action taking place in front of a background of a solid color. You might want to pick up a Chroma Key Screen to shoot in front of if you don't already have one. If not use some fabric or try shooting something in front of a clear blue sky. The second video clip should be whatever you want to use as the background.
Now start up Sony Vegas and insert two video tracks. Put the foreground shot in track 1 and the background in track 2. Now stick the Chroma Keyer as an effect on track 1. Two ways to do this is to either find Chroma Keyer in the Video FX tab and drag it into track 1 or by click the Event FX button on the clip itself and selecting Sony Chroma Keyer.
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Above the preview video turn on "Split Screen View" and set it to FX bypassed. This will give you the track color you want to chroma key on the left side of the video preview and the background on the right.
Now click the Event FX button on track one to open up the Chroma Keyer settings. Under the color select the little eyedropper and use it to select the chroma key color in the left side of the video preview. This will make that color transparent in track 1 allowing whatever your background track to show through.
That's it now play the video and the first video clip is superimposed on the background shot. You can use this with as many tracks as you want, just remember that tracks are layered by their number; for example, whatever is in track 3 will be on top of track 4, and whatever is on track 1 is on top of all tracks below it.
Play around with it and you'll see how powerful this can be, many films are shot entirely against blue or green screen then the background image can be set to whatever the film maker desires, Sci-Fi movies come to mind. You could even film yourself in two separate clips then chroma key them together so that you'd be acting or talking with yourself. As always experiment and good luck with your creative pursuits.
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