Reference
How to Remove a Green Screen in Adobe After Effects
by Alan Donahue
http://smallbusiness.chron.com/remove-green-screen-adobe-after-effects-45682.html
Keylight Plug-In
1. Click once on the green screen video footage to make it active in Adobe After Effects.
2. Click on “Effect,” “Keying” and “Keylight.” This is a plug-in effect for Adobe After Effects that automatically comes with the software.
3. Click on the Effect Controls tab.
4. Select the “Eye dropper” icon next to the Screen Color option. Click on a section of the green screen towards the middle of your video.
5. Click on “View” and select “Status.” Here you can see any parts of the green screen that were not removed. These areas will appear white and gray around the object.
6. Increase the Screen Grain until the outer edges of gray and white disappear and you see just the shape of the object.
7. Play through the video to see the green screen removed.
Color Key Effect
1. Click on the video layer to activate it.
2. Go to “Effect,” “Keying” and select “Color Key.”
3. Click on the Effect Controls tab in the top left of the software. Scroll down until you find the Color Key Effect.
4. Click on the eyedropper tool next to the Color option. Click on the green screen in the Composition Window. Most of the green will disappear.
5. Move the Color Tolerance slider and adjust to remove similar shades of green or darker areas that were cast from shadows and lighting.
6. Adjust the Edge Feather option so that the objects in front of the green screen will blend into the background without rough or glowing edges.
7. Play a preview of the video to ensure that the green screen does not appear throughout the complete timeline. Adjust the Edge Feather and Color Tolerance as needed.