A green screen empowers endless creative possibilities in filmmaking. It's easy to learn how to use a green screen: a shot places actors and their props before a large, bright green backdrop, and in post-production, a process known as chroma key compositing allows any background imaginable to replace the green screen.
Alien worlds? No problem. Atlantis? Let's go.
How does a green screen work?
A green screen powers the chroma key process. Green contrasts well with human skin, so it’s the perfect choice. When editing, chroma keying identifies any chosen color – usually green – and replaces that color with another image or video.
Green screens aren't a high-tech tool. Even an inexpensive green sheet hanging on a wall can accomplish the goal (more on that later). Simply put, a green screen is the tool used to allow for backgrounds to be manipulated post-production.
Green screens work on small and large scales. How did "The Matrix" achieve the slow-motion, bullet-dodging scenes? For the rooftop scene, Keanu Reeves, playing Neo, is tethered to wires hanging from the rafters, allowing him free range of motion to bend in amazing ways while surrounded by a green screen.
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Other examples, like the final battle in "Avengers: Endgame," use green screens to power large-scale visual effects.
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The history of chroma key compositing
Chroma key compositing kicked off in the 20th century. The technique began with a blue screen; pioneers such as Petro Vlahos and Lawrence Butler brought new possibilities with visual effects to the big screen. Films such as "The Thief of Baghdad" (1940) and "Mary Poppins" (1964) showed the industry how to use a green screen.
Around the 1980s, meteorologists began using green screens when presenting forecasts. They used monitors in front of them to help them visualize and point to elements of the radar that viewers should pay attention to.
Chroma key offers more than just creative potential. It provides many practical benefits, including visual uniformity and complete authority over the scene's environment. Green screens eliminate issues like unforeseen weather. This control streamlines the filmmaking process, making production more efficient and reducing the need for extensive location shoots.
DIY green screens
Beginning filmmakers can create magnificent scenes without a full-fledged studio once they learn how to use a green screen. A film taking place in the Sahara desert could be shot in a living room with a green wall (no judgment on paint choice). A few other alternatives make great DIY green screens.
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Fabric or paper
Green fabric and green paper are options for your chroma-key backdrop. The cost varies depending on size, but a beginning filmmaker can quickly get started with less than $100. When it comes to paper vs. fabric, both have their advantages and disadvantages. Paper can be rolled up to avoid wrinkling, although there's no reversing it once it gets wrinkled.
On the other hand, a fabric backdrop will likely come folded and need to be ironed out. Why the emphasis on wrinkles? While they're not the end of the world post-production, they can make using chroma key the first time more challenging.
Paint
Painting a wall green means there's no chance of wrinkles, but it's not always feasible to paint a wall in your office or home. But for those who choose this route, use low-sheen or chroma key paint to reduce reflection, glare, and shadow. Choose a smooth wall, if possible, and layer on the paint. Walls with texture might divert the light weirdly and negatively impact the chroma key in post-production.
Foldable pop-up
A foldable green screen pop-up is an excellent option for those on a budget; plus, it's portable and has little to no wrinkles. The main drawback is that they're small, limiting the scope of the scene a filmmaker might need to capture. They're great for social media videos and for those just getting started.
How to use a green screen in three steps
Once a green screen is purchased and in place, it's time to film. Let's look at the steps needed to film using a green screen:
1. Think through composition and location
Composition is how actors, props, and other elements are arranged within a camera's frame. Understanding it is an excellent first step in learning how to use a green screen well.
First, choose a good location. Consider what the green screen will be used for most. If it's quick videos for a YouTube channel, then a vast room isn't necessary. However, if the goal is to create larger shots and implement special effects post-production, a larger room will make composition easier and less crowded — leading to better shots.
Ideally, there would be enough room for the actors in a scene to stand five feet or more away from the screen.
2. Get lighting right
In film, some things can be easily fixed. Lighting isn't one of them. The goal is to create even lighting across the surface of the green screen. Clamp lights with fluorescent bulbs from a hardware store will work for the beginning filmmaker.
Always light subjects first. Nothing needs to be oversaturated, especially a subject's skin. Doing so can result in weird reflections — if a bright light beams off a forehead and into the heavens, that will distract a viewer. The ideal setup involves a three-point lighting technique:
- Key light: The key light provides the primary light source for the subject. With proper separation from the screen, the key light helps the scene's subject stand out.
- Fill light: Place the fill light opposite from the key light for light balance.A crucial part of learning how to use a green screen is ensuring the subject stands out without casting shadows. The fill light softens the contrast and provides even illumination across the speaker's face.
- Backlight: The backlight helps touch up the subject and further helps diffuse and even out the light.
- Screen lights: These are meant to evenly light the green screen.
Remember, don't overdo the lighting. Keep it simple. Look for “hot spots'' on the green screen. These are areas where the light is more pronounced than in other spots. Make the light even across the screen. Now, it's time to film.
3. Recommended equipment
WeVideo makes learning how to use a green screen easy. Our Apple and Android apps make recording footage simple for the novice filmmaker, even while on the road. Any smartphone suffices in capturing green screen footage, but a digital camera capable of capturing 720p HD footage or above is the best option, if feasible.
Read more: What do you need for your first video shoot?
Editing green screen footage in WeVideo
Once filming is complete, import the video into WeVideo to use our green screen video editor. Those without footage can choose from more than one million stock assets.
With the footage ready, these simple steps make the chroma key process easy:
Step 1: Add footage to the timeline
Drag the green screen footage into the first track on your timeline, and add the intended background in a separate track underneath. This organization ensures proper layering.
Step 2: Open the Clip editor
Double-click on the green screen clip in the green screen footage in the timeline to open the Clip editor. Navigate to the Keying tab.
Select the color picker tool and then click anywhere on the green screen footage to apply the effect.
Step 3 (optional): Adjust the color settings
The green screen effect should automatically apply without the need to adjust the color settings. However, a few options for additional modifications are available:
- Show: Toggle “Show Mask” on to reveal a black and white representation of the mask applied using the color keying tool. Notice that the black area represents transparent sections of the video, while the white area represents opaque sections.
- Color Sensitivity: This smooths out any pixelation and rough edges of color that remain.
- Defringe: This helps reduce color bleeding at the edges of the mask. The left and right sliders control the level of white and black respectively to help match the edges of the mask with a new background color.
Learning how to use a green screen is a vital part of modern filmmaking. There are no limits. Create scenes from anywhere in the world — or beyond — all from the comfort of home. All that’s needed is a space with a green screen, good lighting, a decent camera, and WeVideo's green screen tools!