How can you use keying to remove a shot's background for compositing?

1 Prepare your footage

Before you apply any keying effect, you need to make sure that your footage is suitable for the process. Ideally, you should shoot your subject in front of a solid-colored background, such as a green screen or a blue screen, that contrasts with their clothing and skin tone. The background should be evenly lit and free of shadows, wrinkles, or reflections. You should also avoid any camera movement, zooming, or focus changes that could affect the consistency of the background color. If your footage does not meet these criteria, you may need to fix some issues in post-production, such as cropping, stabilizing, or color correcting.

2 Choose a keying tool

Depending on the software you use for video editing, you may have access to different keying tools or effects. Some of the most common ones are chroma key, luma key, color key, and difference key. Each of these tools has its own advantages and disadvantages, depending on the type and quality of your footage. For example, chroma key works well with green or blue screens, but may struggle with fine details or spill. Luma key works well with black or white backgrounds, but may not be accurate with gradients or noise. Color key works well with any solid color, but may not be precise enough for complex scenes. Difference key works well with static backgrounds, but may not be effective with motion or lighting changes. You should experiment with different keying tools and compare the results to find the best one for your project.

4 Refine the edges

The final step in keying is to refine the edges of your subject to make them blend better with the new background. This may involve applying some filters or effects to improve the appearance and realism of your composite. Some of the most common ones are spill suppression, edge blur, edge feather, and color matching. Spill suppression allows you to remove any unwanted color or light that may have reflected from the original background onto your subject. Edge blur allows you to soften or smooth the edges of your subject to reduce any jaggedness or artifacts. Edge feather allows you to create a gradual transition between the foreground and the background to avoid any hard or unnatural edges. Color matching allows you to adjust the hue, saturation, brightness, and contrast of your subject to match the tone and mood of the new background. You should apply these filters or effects sparingly and carefully to avoid overdoing or ruining your composite.