Everything You Need to Know About Chroma Key and Green Screen Footage

Have you ever wondered why when recording a video, most people use green screen (Chroma Key)?

Green Screen: Technically, this term refers to the colored background you want to make transparent and remove from your shot. This is usually a single colored backdrop, which can be any color, but is usually bright green because it is the color furthest away from human skin tones. (Blue screens were frequently used in the early days with film, and might still be used in certain cases.) Sometimes the term is used as a fit-all for the entire process of keying (see below).

Chroma Key: This popular term goes hand-in-hand with green screen. It’s the actual technique of layering, or compositing two images based on color hues. Every color has a chroma range, hence where the terminology comes from.

Keying: This term is used to describe the process of removing the green screen background in post-production using video editing software. When the green screen background has been keyed, it will be fully transparent. Then you can fill in that transparent area with a different image or video. The goal is to get the cleanest key possible, meaning there are no digital artifacts left on your image where the green screen was original.

Spill: This often refers to the colored light that reflects back onto your subject from the green screen. When a green screen is brightly lit, the light can actually reflect that color back onto your subject. There are a number of steps you can take to prevent spill.

DIY Green Screen

Just slap some fluorescent green paint on a wall and you’re done, right? No, but that’s not far off from your DIY options for green screen. When you’re taking the hand-made approach, it’s all about getting the right material for the backdrop. There’s paint, muslin, nylon, poster board, and more. Think about factors like:

  • Portability – Do you plan to make a studio space, or do you want options on the go? Light, stretchy fabrics are the best for movers and shakers.
  • Patience – Do you have the patience (or time) to spend ironing or steaming out wrinkles from fabric? If so, you can opt for a heavier fabric that wrinkles easily but provides great coverage.
  • Coverage – Are you filming a whole scene, or an up-close subject? The amount of coverage you need will dictate how much material you need. If you just want to cover a small space, a poster board could fit the bill.

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