Blue Screen vs. Green Screen: Uses for Blue and Green Screens

A green screen is a backdrop against which footage is shot to later be superimposed over a separately filmed background, in a visual effects process called “chroma keying.” It is also known as chroma key compositing, color keying, or simply keying. Green screen technology is a central part of this chroma key effect, allowing filmmakers to isolate the actor from their bright green background and then introduce a separate background in post-production—an essential piece of Hollywood movie magic.

A blue screen is a monochromatic background for filmmaking, television, and video production projects. Chroma key compositing, a visual effects (VFX) process, utilizes the blue color to isolate part of the image. This process allows editors to switch the color out for a new image in post-production. In effect, the area where the color appears in the frame becomes a kind of matte that isolates everything that is not the color of the screen, like the actors, details, or parts of a set or location.

Historically, blue screens were more commonly used in special effects. Before the rise of computer-generated imagery, film-based tools such as optical printers made use of blue screens to change backgrounds. Later, with the rise of digital cameras and visual effects, green screens became more popular.

When selecting a green screen or a blue screen, there are various reasons to choose one over the other, depending on the budget, cameras, colors, and costume features of a project. Consider the following:

• Digital: Digital cameras pick up more visual information in the green channel of their image-capturing tech than film cameras. This means you are likely to get a more precise key with less noise with a green screen for digital projects. There is more information available to the camera and to the editing software to get a clean, clear border between the foreground and background.
• Film: A blue screen is preferable for film projects since film cameras capture more detail around the border of the foreground and background.
• Brightness: The color green has a higher luminance value than blue, meaning that it’s both easier to light and that it will bounce more light back toward the camera lens. This makes green screens a better option for low-budget projects, as you won’t need extra lighting. It’s also a better choice for daytime scenes, as the brighter bounce from the keyed-out background is easier to match with the new background. It often makes sense to use blue screens in night scenes, as there will be a less ambient bounce, matching the darker environment.
• Colors in the frame: If you’re working with actors with blonde hair, using green screens can present a challenge. Green has higher luminosity and will reflect light, spilling a green hue onto light-colored, reflective surfaces, like blonde hair. This makes color correction a lengthier process. Blue screens, which have a lower luminosity, will have less color spill. Costume and set departments avoid using bright green and blue hues to make the keying process considerably easier. The green and blue colors in the VFX compositing process vary greatly from human skin tones, so skin tone is not a determining factor when choosing a blue screen or green screen.

Become a better filmmaker with the MasterClass Annual Membership. Gain access to exclusive video lessons taught by the world’s best, including Ron Howard, Ken Burns, Spike Lee, David Lynch, Shonda Rhimes, Martin Scorsese, James Cameron, and more.