To change a white background to transparent in After Effects, you can follow these steps:
1. Open After Effects and create a new composition by clicking on “Composition” and then “New Composition.” Set the desired settings for your composition, such as the frame rate and resolution.
2. Import your video file into the project panel by dragging and dropping it from your computer’s file explorer. Alternatively, you can go to “File” and then “Import” to select your video file.
3. Drag and drop your video file from the project panel onto the timeline. This will create a new layer for your video.
4. With the video layer selected, click on the “Toggle Switches/Modes” button at the bottom of the timeline panel. This will reveal the track matte options.
5. In the track matte options, click on the dropdown menu next to “TrkMat” and select “Alpha Matte.” This will use the transparency information from the layer above to determine the transparency of your video layer.
6. Create a new solid by going to “Layer” and then “New” and selecting “Solid.” Choose a color that contrasts with your video, such as black or red, as this will make it easier to see the transparency.
7. With the solid layer selected, go to the “Effects” panel and search for “Keylight.” Drag and drop the Keylight effect onto the solid layer.
8. In the Keylight effect settings, click on the eyedropper tool next to the “Screen Colour” option. Use this tool to click on the white background of your video. This will key out the white background and make it transparent.
9. Adjust the settings in the Keylight effect to fine-tune the transparency of your video. You can adjust parameters such as Screen Gain and Screen Balance to achieve the desired result.
10. Once you are satisfied with the transparency of your video, go to “Composition” and then “Add to Render Queue.” This will open the render queue panel.
11. In the render queue panel, click on the “Output Module” option and select a format that supports transparency, such as QuickTime with the Animation codec.
12. Under the “Output To” option, choose a location on your computer where you want to save the rendered video.
13. Click on the “Render” button to start rendering your video with the transparent background.
By following these steps, you should be able to change a white background to transparent in After Effects and export/render your video with the transparent background intact.