Green screen video footage, defined.
If you’ve ever seen a film with special effects, whether it’s a creature feature or a science fiction opera, you’ve encountered a green screen. But if it was done well, you probably had no idea. Shooting on location is desirable for many productions, but often, the budget doesn’t allow it. “Filming on location is ideal, but the disadvantage is that you have to bring the whole circus — the crew, actors, trailers and equipment — to where you’re going to shoot,” says director and cinematographer Steven Bernstein.
When you have big ideas but a smaller budget, the green screen will be your best bet.
Green screens let you replace your scene backgrounds with something else, like a different environment or motion graphics. Green screens don’t have to be fancy or sophisticated — the screen itself is often simple green fabric, used because it’s easy to remove and replace in post-production with tools like Adobe Premiere Pro.
Green screens are a subset of chroma keying techniques, which largely refer to the “compositing” or layering of two images or video streams into one another. For example, if you’ve got some brave adventurers crossing a barren landscape, compositing might include laying in a fantasy backdrop or a castle in the background, interlacing it with your talent.
Videos that need green screen backgrounds.
Each film shoot presents its own challenges. Getting every single shot will often be impossible due to budget, location or time constraints. Green screens are powerful tools that allow you to dodge those constraints and tackle a variety of challenges.
Explainer videos and how-tos.
A subject talking to the camera, like in a teaching or explainer video, is perfect for green screen effects. Try compositing in a backdrop of motion graphics or a complementary piece of stock video.
Smaller backgrounds and movement.
If you’re shooting a scene that takes place in a building that has windows or open doors in the background that need removing, a green screen can be a useful tool — especially if the view out the window features a distracting billboard or scenery, for example. For driving sequences (or the interior of a sci-fi cockpit), a green screen is a must to convey motion and a sense of place. Additionally, green screens are often used for phone screens, with the filmmaker creating an overlay for the screen of an iPhone.
Special effects and objects.
Special effects (SFX) artists and cinematographers use green materials on clothing and for motion capture for video that has special effects or computer generated imagery (CGI) creatures, people or animals — a person clothed in green can be replaced with a CG character. When an object or prop needs the application of special effects, objects themselves can be coated in green material for later coverage in post.
As far as selecting the right colour and shade, there’s no standard. Typically, the person responsible for the post-production work prefers a certain shade of green (often called “green screen green”), which is then incorporated into a shot list so the crew getting the footage has the proper information.
When to avoid a green screen.
If you are working with performers, it’s a good idea to use green screens only if you have to or if the green screen forms components of a scene that actors won’t be interacting with. “It isn't easy to act opposite green,” Bernstein explains. It can be difficult for talent to work together with the pieces of the scene if too many of them are represented by abstract green colours and objects. However, if the shoot requires it, make sure to brief the actors.