How to Key Green Screen in After Effects

For best results with keying, make sure that your green screen is evenly well-lit.

Digital video has advanced over the past decade. It really is possible for anyone to shoot video of a subject against a well-lit "green screen" -- which can be as simple as a wall painted bright green -- and then "key" out the green background using Adobe After Effects. A subject can be placed into a new background of your choice, such as a tropical island paradise, a business setting or even outer space. The possibilities are endless. However, keying out a green screen background requires knowledge of a few simple steps.

Things You'll Need

• Adobe After Effects
• Video footage with green screen
• Background of your choice

Instructions

1. Launch After Effects. Create a new project by clicking on "File" followed by "New" and "New Project." Save the new project by choosing "File" followed by "Save." Name the project, and then click "OK." Create a new composition by selecting "Composition" followed by "New Composition." A dialog box appears.

2. Choose the settings for your composition. Under the "Basic" tab, choose your video type under "Preset." Choose your pixel aspect ratio, frame rate and the duration of your project. Click "OK."

3. Import your video footage by clicking "File" followed by "Import" and "File." Navigate to the video file, select it and then click "Open." Your footage now rests inside the project panel on the left side of the screen. Click on the file and drag it down into the composition panel. Your video will appear in the viewer.

4. Select your video layer in the composition panel by clicking on it, and then choose "Effect" followed by "Keying" and "Keylight (1.2)." The effect options appear on the left side of the screen.

5. Click on the "Eyedropper" button to the right of "Screen Color," and then move the eyedropper over the video to click on the green background as close to the main subject as possible. The green background disappears.

6. Fine-tune your key by changing the effect option "View" from "Final Result" to "Status" from the drop-down menu. Twirl down the options for "Screen Matte," and slide the scales of "Clip Black" until your background is as close to solid black as possible. Slide the scales for "Clip White" until your main subject is as close to all white as possible.

7. Change your "View" back to "Final Result" using the drop-down menu.

8. Import your new background into the project by choosing "File" followed by "Import." Navigate to your new background image, choose it and then click "Open." Drag the new file -- which now appears in the project panel -- into the composition panel under the video file.

Tips & Warnings

• For additional tweaking, click on "Effect" followed by "Matte" and "Matte Choker" to see if that further improves your key. Don't overdo it, as the "Matte Choker" is a powerful tool.

Resources

• Adobe After Effects CS5: Keying Effects