Color Fidelity in LED Volumes: Part Two
“LED panels should be doing a lot of the heavy lifting for ambient light, but they’re not meant to be the only lighting source to consider.”
This article originally appeared in AC Jan. 2025.
Craig Kief, ASC led a test shoot in 2021 to quantify the spectral distribution of light cast by LED panels used in virtual production and compare it to cinema lights (The Virtual World, AC Dec. ’21). The test showed that LED panels cast a limited spectral range, contributing to compromised skin-tone rendition and metameric failure (color shifts) in props and wardrobe. The key observation was that because LED panels have only red, green and blue emitters, the gaps in the color spectrum of the light they cast must be filled by wide-spectrum cinema lights in order to deliver optimal color rendition on camera.
“To be fair, none of those panels were designed to emit full-spectrum light,” notes Kief. “They were designed as direct-view video-display devices that look good to the eye and cameras.”
Since that test, several solutions designed to achieve wide-spectrum distribution in an LED volume have been released by ROE Visual, AOTO, Absen and Kino Flo.
ROE Visual’s Carbon 5 MKII (CB5 MKII) RGBW (Red, Green, Blue, White) 5.7mm LED panel includes an extra “white” emitter, and its Carbon CB5 MKII RGBCA (Red, Green, Blue, Cyan, Amber) panel adds cyan and amber emitters.
AOTO has RGBC and RGBW panels in both 2.6mm and 5.7mm densities, and Absen’s Pixel Reality panels (ranging from 1.5- 5.2mm) have RGBW emitters.
Kino Flo’s Mimik, a 10mm hybrid display panel/fixture aims to bridge the gap by providing image-based lighting driven by video signals combined with RGBWW emitters and increased lumen output.
“With these new products, the manufacturers are addressing our use case of virtual production,” Kief notes. He recently tested them against existing RGB display panels to quantify how much improvement there was.
Setting the Conditions
“We shot with four variants, and all of the panels — other than the Mimik — were ROE for consistency, but the spectral variance between manufacturers is minimal, so this is a representative test,” Kief explains. “We tested RGB, RGBW, RGBCA and Mimik using the same methodology as the first color-rendition test,” he continues. “That included three models with different skin tones and fabrics, and real-life objects like fruit.
“We put each device into its best native white by putting a white-light card on the fixture. Then, we measured them with a spectrometer and Sekonic C-800 meter and shot at consistent exposure and camera settings, etc. In post, starting with an Arriraw-to-Rec.709 transform, the 18-percent gray — photographed on the stage — was then measured and balanced to make each iteration match.”
The results of the test confirmed Kief’s expectations. “There was an obvious improvement between RGB and the other variants,” he reports. “The spectrum changes dramatically as we fill in the yellow, the cyan and, to a certain extent, the extreme blues and reds. Skin tones and colors became natural and correct.”
The RGBCA panel and Mimik’s wide-spectrum capabilities showed additional improvement over RGBW. “The rendition is noticeably better, especially when content on the panels is using warmer tones or image-derived off-white content,” says Kief.
Outside the Frame
An important consideration in selecting one of these lighting products vs. a traditional RGB panel is how it will be used — bearing in mind that the RGB+ panels are primarily intended for off-camera use, mostly due to their pixel pitch and a desaturating effect of white emitters when photographed.
Further, Kief explains, “Mimik is a fixture that was never designed to be photographed directly. But besides its excellent color rendition, it’s also much brighter than any LED video panel. So, it’s better to think of it as a lighting fixture that displays video than a video panel with high-quality light emission.”
The Immediate Future
Would it be advisable for an existing LED volume to upgrade its ceiling panels to these newer models? “In the immediate future, considering the global film-industry contraction,” Kief says, “these products are probably most advantageous for new volume builds, or for the rapid-build volume tailored for an individual production, or perhaps for car-process environments, because they’re smaller than a full volume build. Another great immediate application for RGB+ would be rolling walls to create supplemental lighting sources.”
“Cinema Lighting Remains Essential”
Representatives from manufacturers of RGB+ products shared some observations with AC.
“Lessons from the lighting industry are clear,” says ASC associate member Tucker Downs, R&D manager and color scientist at ROE Visual. “To capture quality images on camera, you need quality lighting on set. In virtual production today, cinema lighting remains essential. Without direct lighting, severe color distortion affects much of the set.
“It’s important to understand why virtual production exists,” he adds. “[One of the goals] is to re-create the ambient light field of another location on set, allowing us to shoot as if on location while maintaining creative and weather control.”
Bryan Larason, a business manager at AOTO, concurs, noting, “RGBW offers the superior configuration with balanced light output for cinematic builds — but you need to ensure you’re using additional cinema lights for proper color balance. Practical lighting remains essential regard-less of advancements in panel technology.”
Frieder Hochheim, Kino Flo president and ASC associate member, sees these new products as fulfilling a longstanding need. “We’ve always aimed to achieve certain visual goals and have often compromised on color fidelity and synchronization,” he says. “The challenge has always been to reach a level where [they] are no longer compromised. Mimik allows us to achieve what we’ve only hoped for in the past.”
Daniel Warner, technical pro-duction supervisor at Megapixel and an ASC associate member, also weighed in on Kief’s test. “Natural lighting conditions span a wide range of Kelvin temperatures, so technology should enable true-to-life color for any time of day or environment,” he notes.
“Cinematographers need a broad light spectrum to film scenes such as sunsets and blue-sky daytime. Using wide-spectrum warm white and cool white or amber and cyan LEDs accurately replicates conditions from 2,700K to 15,000K.”
Filling in the Spectrum
The critical takeaway is that the cinematographer, production de-signer, set decorator, costumers and other key creatives must be aware of the color spectrum within a volume, because it will directly impact the choices they make.
Kief notes that the need for supplemental lighting in a volume is not that different from the need to mix tungsten, HMI and fluorescent sources on traditional sets. “LED panels should be doing a lot of the heavy lifting for ambient light, but they’re not meant to be the only lighting source to consider,” he says. “Even if you bring in ceilings and supplemental RGBW/RGBCA panels or Mimiks, we’ll always need cinema lighting to accentuate shape, contrast and texture.
“By far, the main advantage to a cinematographer for shooting on a volume,” he continues, “is to let the environmental lighting create a better blend with the virtual elements instead of trying to light the real-world elements for some-thing that doesn’t exist yet. And these wider-spectrum panels/fixtures help us achieve that goal with far better accuracy. We’ve had to use various schemes to work around the lack of full spectrum and resulting color shifts — like testing and changing colors in the art department to reduce shifts; desaturating the red channel on the panels, which works a little bit; or turning off or ND-light-carding panels — and now we’ll have to do far less of that.
“Everything will fall in line naturally the more you can fill in the spectrum in the volume with these new tools. Understanding that when going into a virtual production is very important for cinematographers.”
Part One of this report can be found here.
