Digital keying effects are used in virtually every form of film-making or video production today. Whether you are shooting the next “Avatar” or are a prolific YouTube content creator, you probably use this special effect technique to combine or overlay images and footage together into one seamless composite. And you may wrestle with the decision over which color of keying background to select and what keying surface to use.
What is Keying?
Keying (also known as compositing) combines visual elements from separate sources into a single image. This creates the illusion that all those elements are part of the same scene.
The technique requires the use of a uniformly-colored keying backdrop, such as a "green screen" to achieve the effect. Through the magic of compositing or keying software such as Fusion™ or Nuke™, the green colored items in the scene (the keying backdrop) become transparent. This allows an editor to insert a different background in its place (a street scene, a mountain, etc.).
Color Options for Keying
With today’s advanced compositing software, you could technically pull a key from almost any color background. But the majority of effects are shot against either a solid blue or green background. To complicate matters, these color standards are available in two basic flavors: Chroma Key (Green or Blue) and Digital (Green or Blue). The Chroma Key colors are a darker shade and duller color. The Digital colors are much brighter with a purer color hue.
What Determines Color Choice?
The decision is usually determined by what’s being shot, how you’re shooting it, and what type of final scene is being composited. You’ll need to consider:
- The colors of the costume, wardrobe and other elements in the shot
- The subject’s proximity to the backdrop screen
- The level of detail that needs to be separated from the background color
If your subject contains a lot of blue or green then selecting to key against a blue or green background is an easy decision. Choose the background color which appears least in your subject, either in the costumes or scenic elements. If the subject does not clearly dictate the choice, then most professionals today choose to key in front of green rather than blue. But either way, this choice is yours and you can get an excellent key in front of either color.
When to Choose Digital
When possible, it’s recommended to choose Digital Green or Digital Blue. The brighter and purer hue in digital colors allows more separation between your subject and the background.
If your subject contains very fine details that need to transfer – like fine hair, wisps of smoke, or cast shadows – then the bright, clean separation between the subject and background using Digital Green is crucial.
When to Choose Chroma
If your subject is close to the background, choose the duller, Chroma option. The brightness of the Digital color is much more reflective than the darker Chroma Key colors. If subjects are too close to the background, you may see the background color reflect and spill on the subject. This spill can create a halo of colored light on your subject that computer software will interpret as background and eliminate in the final key.
PRO TIP: If you experience a halo effect in a well-lit composite shot, try backlighting your subject with the complementary color of the background – Amber backlight in front of Digital Blue and Pale Magenta backlight in front of a Digital Green background. Or, use Chroma Key instead where the darker color is less likely to reflect a colored halo into your subject.
Choosing the Right Keying Surface
Rose Brand offers a wide range of materials to meet you budget, your technical requirements, and the physical constraints of your location when it comes to choosing a keying surface. Here are some product options:
Fabrics as wide as 10ft seamless are available in Digital and Chroma Key colors. Make your selection based on price and size, keeping in mind that a fabric background must be stretched wrinkle free in order to pull a clean key. Other factors in your choice will be FR rating, color choice, and reflectance. A matte finish is best for close work, while a slight sheen can help with separation between subject and background. Browse Keying Fabric
Floors and Curves
A Chroma Key vinyl floor may offer the best solution for a studio that will get moderate use and where continual repainting the floor would create a logistical difficulty or be too expense. Chroma Key Floor is 63in wide and double sided with Chroma Key Blue on one side and Chroma Key Green on the other. In addition to providing a durable floor, the vinyl can also be used to create a continuous scoop from wall to floor which eliminates the “corner” where floor meets wall. This intersection often creates a difficult area where a green screen and green floor don’t match nicely. Creating a scoop prevents the shadowed region where floor meets wall and that is often difficult to key out. Browse Keying Floor
Paint the Wall
Chroma Key Blue, Chroma Key Green, Digicomp HD Green, Digicomp HD Blue all make an excellent keying background. With proper preparation, these paints can even be used on the floor for short term shots with light traffic. One limitation to a painted Digital Green wall is the expense of the paint and that the wall cannot be moved with you. Browse Keying Paints
If you have any questions about the best keying backdrop to use for your shoot, please don’t hesitate to send us an firstname.lastname@example.org or call us at 800.223.1624.