A great skill to have as a video editor (and general video creator) is to know how to use green screen footage. Shooting with a green screen allows you to insert video of an object or person on top of another layer of video – basically inserting the person into a new scene.
Before we learn how to edit green screen footage, let’s look a little deeper into what green screen footage is, and why we use it.
The definition of chroma keying (another work for the use of green screen – or really any colored backdrop that will later be removed) reads as follows: Chroma key compositing, or chroma keying, is a special effects / post-production technique for compositing (layering) two images or videostreams together based on color hues (chroma range). The technique has been used heavily in many fields to remove a background from the subject of a photo or video – particularly the newscasting, motion picture and videogame industries.
You’ve probably been watching chroma keyed video for a long time. Most Hollywood films have some sort of video compositing. You think Hogwarts actually exists? I wish! Most of those backdrops and sets were completely digital. A common use of green screen is during weather forecasts.
How does green screen work? You position your subject in front of a green backdrop. In post production, you use effects to remove the green parts of your video frame. Your video editing software basically reads all of the data in your frame, and whatever pixels land in the chroma keyed color (could be green or really any color you want) are deleted.
Why use green? The semi-neon-green that is used in green screens is a color that is not common in nature. So you won’t worry about people showing up in a neon green shirt to work (see green screen fail below). Green is also a color that cameras are very sensitive to. Green is also easier to illuminate than other colors – so less light is needed to create a solid green backdrop with no shadows.
Watch and learn: Green Screen Editing Tutorial
How do you edit green screen footage?
Adobe Premiere Pro has a solid set of tools to edit green screen footage with. You will find them in the Effects tab, under Video Effects, and Keying. There is a basic Color Key and the Ultra Key. Both work in a similar way, but the Ultra Key is what I prefer to use.
Steps to using the Ultra Key
- Add green screen footage to your sequence.
- Drop the Ultra Key effect onto your clip
- Go to the effects control tab
- Use the eyedropper to select the green color on your video frame (click somewhere near your subject). You may have to try this a few times to get the best key.
- Use the Setting option to choose how aggressive the effect works.
- Play with the numbers under Matte Generation until all the ‘noise’ is gone. Usually your green screen backdrop isn’t perfect. So shadows and highlights won’t be ‘keyed out’ until you make adjustments with the Matte Generation.
- Use the Matte Cleanup options to affect the edges of your objects. Choke will shrink the edges, while Soften will make the edges more fuzzy.
- Use Spill Suppression to adjust the edge colors of your subject. Sometimes when shooting in front a green screen, a green reflection will make your subject appear slightly tinted green. Spill Suppression can fix this problem.
Step 2-3 – add the Ultra Key effect to your clip
Step 4 – Use the eyedropper to select the green
Step 5 – Choose a setting – try aggressive!
If you’re having issues with not being able to get rid of all of the green in your background, try selecting a different ‘Key Color’ with the eyedropper. First try selecting a darker part of the green. Then if that doesn’t work, try a lighter part. I usually find that selecting the darker part of the green first works best.
Cropping can be your friend. Sometimes you don’t need to eliminate all of the background because you can just crop it out using the Crop effect. This way, you only have to focus on chroma keying the area right around your subject. The rest of the frame can just be cropped out. Just make sure that your subject or any part of your subject never gets cropped out of frame. This is easiest if your subject isn’t moving around.
If none of this works, you might have to re-shoot. It is really difficult to shoot green screen video. They goal is to have a flat background with no shadows (i.e. the background has to be the same brightness).
By now, I hope you have a great idea of how to use green screen footage, and how to edit it in Adobe Premiere Pro. If you have any questions, leave a comment below. To learn more about editing green screen video, I have a complete course that will teach you how to do so in Adobe Premiere Pro, After Effects, Final Cut Pro 7, and Final Cut Pro X.
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