Get the ASC’s Practical Advice on Lighting for LED Stages

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It’s essential that directors of photography who delve into this milieu become familiar with its methods of illumination.

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As LED walls become part of the arsenal of filmmakers, the nuances of lighting photography are becoming apparent. The idea that the LED screens themselves can illuminate the actors and set is broadly true but masks a maze of complications and decisions that the cinematographer and gaffer have to master.

The American Society of Cinematographers has come to the rescue with a timely user guide for lighting for LED stages.

There are different types of LED walls or walls systems which, in any case, can be configured differently for each show.

“The fundamental premise is that the images appearing on these walls are displayed via LED panels, which create varying degrees of emissive lighting, while additional lighting on actors and physical objects can come from LED ceilings or sidewalls, practical lights, and movie light,” says Noah Kadner, virtual production editor for the organization’s magazine, American Cinematographer. “Combining these tools can deliver highly realistic results.”

Now, let’s get into it.

Standalone-Style LED Environment

In a standalone-style LED-screen environment, the primary screen’s content can be synchronized with other, off-camera LED screens to create additional reflections and interactive lighting effects. Via the Digital Multiplex (DMX) network protocol, the “kinetic lightning,” which can imitate the lighting effects of the content that appears in-camera, is also able to be synced into the system. For example, when a streetlight passes by in the background footage on the screen, a lighting instrument can perfectly match its hue and intensity.

Kadner explains that the DMX control in such a setup can be driven either by “pixel mapping” or by manually programming specific patterns or effects. These options would be accomplished with, respectively, pixel-mapping software or a dimmer board. Pixel mapping is a process that samples the hue and intensity of the source footage and then, via DMX, sends those values to the lights.

Full LED Enclosure Environments

Designed to create immersive environments, these stages typically have large, curved screens with ceiling panels and full side panels.

“Because the screens encompass the entire set, LED-enclosed volumes generate a large amount of interactive, emissive lighting solely from the screen content. Cinematographers can select the quality of the overhead sky fill, adjust its color and saturation, and then adjust any other virtual lighting sources, such as VFX-generated practical fixtures within the virtual sets.”

Since a significant degree of additional customization is possible on set, it’s important to determine beforehand which elements of the on-screen content will have this level of malleability. This is coordinated through the virtual-production supervisor and the brain-bar team.

There’s a new lexicon developing here. The virtual production supervisor serves as the liaison between the cinematographer, gaffer, and virtual content to provide virtual lighting tools that augment the interactive content. The brain-bar crew handles all the onscreen content, taking the tracking data, integrating it to Unreal Engine, and exporting the imagery back to the screen.

Control in the Volume

An LED volume comprises hundreds or thousands of LED panels that can each be addressed individually. Kadner explains how portions of LED surfaces which are out of view of the camera, such as the ceiling, side walls, or any section that’s not actively being captured, can run at higher or lower brightness levels, or be manipulated in any number of ways to create specific reflection effects on, for example, a vehicle or costume.

From Silks to SkyPanels, VFX simulations of movie lights can also be created on the screens of the LED volume as off-camera effects. Virtual negative fill can be designed and incorporated into LED screens. These virtual light effects are fed to the screens via software like Unreal Engine, MadMapper, Disguise, ILM’s StageCraft and Helios, DaVinci Resolve, Zero Density, Mo-Sys VP Pro, or Notch — all of which factor in the entire volume’s geometry.

“The process of adjusting the lighting tools on the LED wall to create virtual fill and negative fill is remarkably fast and incredibly versatile,” says the ASC’s Matthew Jensen, who shot three episodes of the second season of The Mandalorian. “While shooting close-ups, I often [virtually] neg entire walls of the content while adding a bit of sparkle to an actor’s eyes with virtual fill. We can change the shapes of these virtual flags and sources, or [their] colors, to match a particular light in the content with ease. I’m usually accompanied by someone from the brain bar who’s holding an iPad with all the virtual tools at their fingertips.”

As the screens’ emissive lighting is relatively soft, movie lights like Fresnels can be brought in to simulate the hard light of the sun or other hard sources. Watch out for light contamination from practical lighting falling directly on to the LEDs. It can wash out the image or reflect the source on the screen itself.

“Depending on the reflectivity of the screens you’re using, something [as minor as] a candle, a bounce card — or even other parts of the volume — can reflect,” warns the ASC’s Craig Kief. “I equate our challenges to the growing pains during the early days of digital capture or LED lighting equipment. This technology is already great, but it’s still very emerging, and its potential is incredible.”