The CRI Issue

Just a few short years ago, LED (light-emitting diode) lighting technology seemed poised to take over lighting for film and television. The technology promised significantly greater energy and heat efficiency than existing technologies. LEDs required much less power, were cool to the touch, didn’t heat up sets and, in general, seemed to be the way of the future. Yet here we are a few years later and massive arrays of LED lights are still missing from feature film sets. What happened?

Unlike the film business, LED lighting has made sizable inroads into the television and news markets—lighting directors and station managers point to LEDs’ relatively low energy consumption and lack of heat output—but if you visit a feature film set these days, you’re likely to encounter traditional Tungsten, HMI and fluorescent lighting much more often than you’ll see LEDs, especially when it comes to lighting talent rather than sets.

Until just a few years ago, the most commonly available LED lighting products were panel lights, based upon inexpensive 5mm bulbs sourced from various Chinese manufacturers. When LED lighting for image creation came to market a few years ago, there were no open-face single-source LED lights available and no LED Fresnels, limiting how cinematographers and lighting directors could artistically utilize the technology.

On the first-generation LED panels, the light cast by hundreds of individual LED bulbs resulted in strange shadows when lighting talent, especially faces, necessitating either bouncing the panels into a reflector or diffusing the light through a soft box or an umbrella, reducing the already modest light output of the panels even further. Relatively low output could be accommodated by doubling up on panels, but there were still other downsides that have proved difficult for cinematographers to work around.

The first-generation LED panels had a low color rendering index (CRI), a quantitative measure of the ability of a light source to reveal the color of various objects faithfully in comparison with an ideal or a natural light source. Without high CRI, skin tones can appear unnatural and difficult to color correct because portions of the light spectrum are either missing or disproportionately high. The first generation of 5mm LEDs had a high level of green output sometimes, depending on the how the camera was white-balanced, resulting in greenish, unnatural skin tones. The first-generation LEDs also had relatively low output in relation to cost. Colors shifted when the lights were dimmed. These were all limitations that manufacturers set out to resolve.

The second generation of pro LED lighting has begun hitting the market from key players like ARRI, Cineo, Creamsource, Litepanels and many others. High-quality Fresnel and open-face instruments have appeared. The appeal of LED lighting has grown as the products have evolved. The new lights have greater output, utility and ease of use. Most importantly, the CRI for the second generation of LED lighting has increased significantly, with most of the new LEDs boasting CRI ratings as high as 95.

The CRI Issue
TOP: Cineo Lighting’s TruColor LS delivers a soft light optimized for image capture, with an extended CRI of over 95. ABOVE: Cineo’s Remote Phosphor Technology eliminates the color-accuracy limitations found in most LED lights.

LED manufacturers have developed and refined their own individual technologies for increasing CRI. Cineo Lighting manufactures several models of the next generation of LEDs, utilizing a design called RPT, or Remote Phosphor Technology, to significantly increase CRI. Instead of relying on the LEDs as the direct source of illumination, TruColor fixtures rely on a separate phosphor substrate to emit high-quality predictable light when excited by the high-frequency wavelengths from blue LEDs. The result is a continuous linear spectrum that’s unlike any other digital light. RPT employs a transparent surface onto which a special phosphor coating is applied. These phosphors are excited at two precise wavelengths, in this case, with LEDs completely separated from the phosphor substrate, resulting in very stable high-CRI white lights.

“With Remote Phosphor Technology, our lights have really high CRI, accurate and consistent color rendering with very close color matching from fixture to fixture,” says Rich Pierceall, CEO of Cineo Lighting. “We don’t run into problems like the traditional LED fixtures have had with these areas. The biggest testament to these claims is the number of feature films our lights have been used on recently. We have really great A-list DPs in the film industry helping us to establish RPT technology into the motion picture business.”

New technology not withstanding, why do many feature film cinematographers still seem hesitant to wholeheartedly embrace LED technology, particularly for lighting talent? As a longtime manufacturer of tungsten and HMI lighting, as well as their recent development of cutting-edge LED Fresnel lighting, ARRI is in a unique position to receive unbiased feedback from their customers since ARRI can supply them with traditional Tungsten and HMI products, as well as cutting-edge modern instruments like ARRI’s LED Fresnel lights.

Notes John Gresch, VP Lighting Products, ARRI Inc., “Often, cinematographers and gaffers tend to work with instruments that they have worked with for years because they know exactly what the instrument will do and how the light it produces will react. One reason some cinematographers steer away from using LEDs is that they don’t get the color quality they’re looking for, combined with the output level they need for a particular situation.”

In speaking with manufacturers and users, there doesn’t seem to be a hard and fast answer as to why feature films have been slower to embrace LED technology than their television brethren. Based upon conversations with several cinematographers, gaffers and manufacturers, it appears that as the technology behind LED lighting continues to evolve, and output and color accuracy increase, more and more feature film cinematographers and gaffers are warming to the idea of putting LED lighting to work. Fulfilling the director’s vision to produce compelling images can go hand in hand with lower power consumption, efforts to be more green and reducing the need for air conditioning to keep sets, crew and actors cool.

Stay tuned for the first studio feature film to be completely lit by only LED lighting technology; by all accounts, it will be happening momentarily.