During the Olympics, the BBC and NBC studios used PRG Trucolor HS fixtures with Intematix ChromaLit panels to deliver up to 98 CRI at color temperature of 3200K. If you watched any of the recent Olympics TV coverage and thought you noticed better color rendering than in Olympics past, you are not mistaken. Both the BBC and NBC studios this year were lit by Trucolor HS fixtures from Production Resource Group (PRG LLC), blue LED-based luminaires with high-CRI ChromaLit panels from Intematix that allow up to 98 CRI at a color temperature of 3200K. "Color rendering is absolutely critical, since the camera can only accurately see color if the spectrum in the light source is complete. Typically, skin tone suffers when R9 and R13 are not above 90 CRI," said Rich Pierceall, director of digital lighting sales with PRG, based on Armonk, NY. The Trucolor HS achieves extended CRI measurements of 94 for 5600K daylight and 98 for 3200K. According to Pierceall, the best integrated phosphor-LED fixtures on the market range from 88-92 CRI.
Steve Brill, president of Lighting Design Group in New York, NY, used the PRG Trucolor HS fixtures for the first time at the NBC Wimbledon and Athletics studios. The fixtures, designed for motion picture and broadcast productions, have exchangeable remote-phosphor panels, allowing the user to quickly change between color temperatures. "These fixtures turned out to be excellent replacements for traditional soft lights. The ability to change color temperature was a great plus for us, especially at the Wimbledon windowed studio," said Brill. This video demonstrates panel change-out.
Brill added "One of the challenges with LED fixtures has always been intensity and color. This fixture is actually significantly brighter than the tungsten fixture it replaces, and both the color temperature and color rendering index are excellent." The light emitted from the fixture is distributed at 160°. Regarding the type of light provided, Brill commented "It provides a very soft, flattering light, with excellent color and without multiple shadows. There is no need to add diffusion, which cuts down on light output." Output of the LED-based fixture is 20,000 lm and it requires 400W of power. The light output is roughly twice that of a 2000W tungsten incandescent bulb.
Recently, at The LED Show in Los Vegas, Julian Carey, senior director of marketing at Intematix, based in Fremont, CA, explained the mixture of phosphors that allow such high CRIs. He said that there are four families of phosphor materials, based on silicates, garnet, nitrides, and aluminates. "Green aluminate phosphors can achieve a broad spectrum and are a great compliment to red nitrides that deliver the high CRI and R9 combination," said Carey.
Intematix's patented remote-phosphor approach is ideally suited to non-directional lighting applications such as area or ambient lighting. By separating the remote-phosphor panel from the blue LEDs (rather than coating the LED with phosphor), higher system efficacy can be attained because light extraction is higher and the system operating temperature is lower (50°C, for instance, in the PRG fixture). Carey explained that up to 30% improvement in system efficacy is possible using a remote-phosphor approach versus LEDs with phosphor coating.
Intematix and PRG began exploring high-CRI ChromaLit panels in May of 2011 to meet the very high CRI requirements of the film and television markets. The phosphor mixture for a specific CCT is coated on the polycarbonate panel. Now, the exchangeable panels can meet the variety of CCT needs for photography: 2700K, 3200K, 4300K, and 5600K individual panels as well as and specialized panels for use on green screen stages, which spectral output between 520 and 550 nm. The panels are available in sets of two for $395 to $695 per set. The fixture itself is priced at $3750 with a lifetime specification of 35,000 hours for L70.
"PRG's TruColor HS light fixture showcases a stunning and functional implementation of ChromaLit," said Intematix's Carey. "Working with PRG, we get to see the light quality and efficacy advantages of our product come to life in an exacting new application."
