Experts on the Limits of RGB and Benefits of Multi-Primaries

TMS Consulting president Jim DeFilippis, who co-chaired the 6P Color program with Baylor University senior research scientist Gary Mandle as part of the SMPTE+ Series, moderated a discussion about the limits of the RGB color system. XStream member Gary Feather focused on display technology, noting that manufacturers have solved brightness and resolution issues for displays, but not color gamut. “It’s complex,” he said. “But color gamut has headroom to expand” to offer a better toolset for storytelling. “Let’s take that step to move beyond the [RGB] triangle,” he urged.

Feather added that laser phosphor, DLP, dvLED and OLED are all displays that can replicate multi-primary color displays. “It’s an implemental — not new — technology,” he explained. “Displays will not constrain the 6P vision described here.”

Cinematographer David Stump, ASC, who is also chair of the Camera Committee and Metadata Committee of the ASC Motion Imaging Technology Council, reported that, “every camera made today in the digital realm has its own color gamut.”

“Those gamuts are not exactly the color gamuts we use for display or projection,” he added. “They’re camera-native gamuts, made up of loose, fuzzy primaries of dyes on sensors. The de-Bayering of the RGB primaries has to synthesize secondary colors from the crossover areas in the curves. While it’s a fairly big gamut, it doesn’t encompass what the human eye sees — not even close.”

“Multi-color primary gives us a huge ability to present more subtle hues and gradients of hues, both in recording and display,” Stump added.

He also noted that, although it will take time to incorporate a multi-spectral approach to capture and display in other portions of the workflow, it promises to have a most profound impact in “the representation of human skin.” He encouraged everyone in the industry to take into account that digital cinema is still evolving. “There can be a fatigue in learning new technology,” he said. “But digital cinema is not done.”

BBC R&D’s Richard Salmon tied together issues of cameras and displays by describing how a multi-primary color gamut would impact the entire broadcast image chain, from studio to the home viewer. At Rochester Institute of Technology’s Center for Media, Arts, Games, Interaction & Creativity (MAGIC), director David Long described his facility’s research into “fully spectral workflows.”

“It would solve many problems and would be able to replicate the imagery captured,” he said. “Expanding to a spectral domain enables legitimate color enhancement that includes an enlarged color gamut, enhanced color accuracy, and greater creative palettes for color correction.”

Mitch Bogdanowicz, president of MJB Consulting and former long-time Kodak senior research fellow noted the “definite advantage” of potential multi-primary color spaces: “expanded color space, less gamut remapping required and largest color space for mastering.” “The other nice part is that you’re filling in the gaps between the narrow primaries and offering a more fluid curve shape,” he said. “It’s easier to observe.”