Virtual production is changing how filmmakers tell on-screen stories.
Within this transformation are two pieces of technology: green screens and LED screens – the old and the new.
Both help create vivid, dynamic environments for on-screen narratives but operate very differently.
While they fulfil similar roles in the production process, choosing between these technologies significantly impacts the creative and logistical approaches to filmmaking.
Ultimately, it comes down to a project's creative and logistical needs and goals. So, what are each technology's strengths and weaknesses, and how are they transforming the filmmaking process?
Virtual Production Green screens
Green screens help create virtual backgrounds in a film. A large, bright green backdrop stands behind the filmed subjects, which editors later swap for a different background in post-production.
Well, that’s traditionally how they’ve been used.
Green is used because it's vivid and does not match any natural skin tone or hair colour, making it easier to isolate the subject from the background during editing and in real time. This technique is called chroma keying, in which the green colour is keyed out to overlay the foreground subjects in an animated computer-generated 3D or still 2D image background.
Green screens (or blue screens) have been a staple in the film and television industry for over 70 years because of their creative flexibility. They enable filmmakers to create environments and scenarios that would otherwise be impossible, impractical, or too expensive to shoot.
Working with a green screen begins during the filming stage, where lighting plays a crucial role in ensuring the green backdrop is lit correctly, without tones, shadows or wrinkles, which complicates the keying and post-production process.
One traditional challenge of using chroma keying while filming is that the actors, directors, and DPs require a lot of imagination as they have to imagine the environment. However, by utilising broadcasting technology’s live chroma keying, both the foreground and background plates can be ‘composited’ (meaning put together) live and displayed on monitors.
With accurate camera tracking in Unreal Engine (a game development platform from EPIC games), filmmakers can create a digital twin of a physical camera and lens in a 3D CGI environment. This allows the physical and digital to move, zoom and focus in perfect synchronisation.
By using separate elements for the foreground (captured with a physical camera) and the background (created with CGI), we can composite them live-to-tape. This method allows for on-set pre-visualisation or the creation of a rapid rough cut without requiring extensive post-production work to combine the elements of the rushes.
Other advantages include additional cameras (which help with non-script or improv) and shooting isolated camera plates with camera and lens telemetry (movement, focus, zoom), which allows for more traditional post-production.
In the latter scenario, the footage moves to post-production, where visual effects artists use software to remove the green background and replace it with the desired digital or pre-filmed backdrop.
This process requires precision and attention to detail to seamlessly blend the foreground subjects and the new background, ensuring the final output is believable and immersive. The post-production process is significantly simplified because the camera and lens information is recorded in advance, saving time and budget.
A further advantage is that green screens are, by nature, a cost-effective way to use virtual production and are not limited to high-budget productions. Therefore, they are accessible to independent filmmakers, content creators, and educators when the previs is more than adequate for the final footage.
This accessibility has democratised the production process, enabling creators at all levels to experiment with visual storytelling and bring their imaginative visions to life.
LED screens
Like green screens, an LED screen is a technology filmmakers and content creators use to create backgrounds for scenes. Unlike green screens, which may require post-production work, LED screens provide a real-time backdrop that can display intricate, dynamic scenes and landscapes. This is also called ‘in-camera VFX’ or ICVFX.
However, using LED walls for film is newer.
On a film stage, a wall of LED panels is volume. Each panel consists of many small light-emitting diodes that can display high-resolution images, videos, and 2.5D and 3D environments directly on set – for example, a Martian landscape, a moving video filmed from a vehicle, a Parisian cafe, a highly stylised hotel reception, or even a field of lollipops and cartoon giraffes.
These can be static or live and interactive backgrounds that enable directors and cinematographers to capture complex visual effects in-camera.
One of the most notable advantages of using LED screens in virtual production is the ability to simulate different lighting conditions and environmental effects in real time, especially when reflections (like on a car) or transparency (like in a bottle of liquid) are key.
This is particularly helpful for scenes that require specific times of day or weather conditions, which would be logistically impossible to replicate on location. For example, you can shoot all day at golden hour.
LED technology has opened up new avenues for creativity and storytelling. By using real-time rendering engines, such as Unreal Engine, filmmakers can instantly create and modify complex digital environments, allowing for massive flexibility and experimentation during filming.
Though there are some limitations, this capability saves time and resources and empowers directors and visual effects teams to push the boundaries of what is possible within the visual narrative space.
But does it have to be one or the other?
LED is a joy to film with. Scenes based in Mexico, Malaysia and the Moon can all be filmed in a studio in Manchester, UK. It’s not only more fun to film this way, but also much more environmentally friendly!
At the same time, shooting with chroma keying is considerably more flexible and cost-effective than LED – but you are filming with a blank green wall. Flexibility comes in multiple cameras, camera/lens data, easy-to-shoot wide shots, and far less tech if a lot of post-production is planned or ultra-high production values aren’t required.
However, it’s not a zero-sum decision; many modern filmmakers will mix both.
"The Contractor" (a joint Screenography and Mo-Sys production) TV pilot exemplifies the hybrid approach, mixing a VP green screen and VP LED based in the same studio to remarkable effect. This method allowed the production team to simulate diverse New York locations shot from their London studio, bypassing the logistical nightmares and costs of on-location shoots in New York.
Green screens provided flexibility for wide shots where interaction with the environment and accurate shadow depiction were crucial. This allowed for higher resolution renders to be produced after the shoot, and composited in post production. As the camera and lens metadata was captured on-set, this also significantly reduced time, as photography and background movements were perfectly in sync.
Conversely, an LED wall was employed for close-ups and mid-shots, capitalising on its ability to deliver highly realistic backdrops and lighting effects that interact directly with the performers and the camera.
The technical setup for "The Contractor" was designed to harness both technologies' strengths. Identical cameras and lenses were used for both green screen and LED wall setups, while advanced lens distortion matching techniques allowed for seamless integration of virtual and real elements.
Pre-production played a pivotal role in the hybrid approach's success. Extensive planning and scene optimisation enabled a smooth transition between the two technologies, allowing the production to adapt to the demands of each scene without affecting quality or efficiency.
Moving forward
The choice between green and LED screens is not a matter of superiority but of strategic selection based on the project's specific needs and creative goals.
This hybrid approach underscores the principles of virtual production, where the creative and logistical applications of green screens and LED screens are seen not as mutually exclusive but as complementary tools that can be integrated to enhance the filmmaking process.
As virtual production continues redefining filmmaking possibilities, embracing each technology's unique advantages will be key to unlocking new creativity and narrative expression dimensions.