The dust has yet to settle on the argument over whether LEDs are suitable for museum lighting. In his Jan/Feb 2011 ARCHITECTURAL LIGHTING article “Museum Lighting in the Second Decade of the 21st Century,” Kevan Shaw, design director of Edinburgh, Scotland–based KSLD noted that while LED technology has advanced, it was not ready to “replace the best low-voltage tungsten halogen lamps, and limitations in the technology may prevent us from getting there.” To reduce energy usage, he added, museums “might have to accept a loss in lighting quality” or increase restrictions on exposure times and lighting controls.
While lighting and conservation experts generally agree that no silver bullet has emerged in the past year, they do note that museums' willingness to explore LED source and fixture options has increased significantly. Solid-state lighting is where manufacturers' research and development dollars will continue to flow, and it is likely that museum settings will be part of the discussion.
Performance Matters As more art museums open their doors to LED testing, both the technology's potential and its limitations are moving from speculation to observation. Five years ago, Daniel Gelman, president of Lighting Services Inc in Stony Point, N.Y., was an LED skeptic. “It was difficult for me to first grasp LEDs and buy into it, as a company,” he says. After visiting several test sites, he had a watershed moment when he heard a curator comment, “I've looked at this painting for the last 15 years and I haven't seen some of this detail that I'm seeing now.”
Matthew Siegel, chair of conservation and collections management at the Museum of Fine Arts (MFA) in Boston, agrees that LED developments in recent years “have been fast and furious.” With white LEDs' color-rendering indexes now in the mid-80s and 90s, Siegal says, “The products are [now] to [a point] where it is reasonable to step in.”
Though LED efficacies now surpass 100 Lm/W, Shaw says that with high-quality color rendering comes sacrifices in energy performance. “We're still not seeing much better than the best products ranging between 40 and 60 Lm/W for a high-quality color-rendering device, and 60 to 70 Lm/W for a less-high-quality color-rendering device.”
Lighting manufacturers have balanced out the high blue peaks in early LEDs' spectral power-distribution curves, which have the potential to fade yellow-colored dyes.
Clint Paugh, lighting designer at the Nelson-Atkins Museum of Art in Kansas City, Mo., wishes that manufacturers would focus less on illuminance and more on improving retrofit products. “Their selling point is more light for less, but we want less light for less,” he says. (Paugh generally doesn't light anything over 25 footcandles in the museum.)
However, LEDs have made some strides in flexibility, says David Clinard, principal at Clinard Design Studio in New York. Fixtures “cool enough to touch in front of the light source” have given designers greater control through the use of media such as color-filtering gels and holographic films. For display lighting, fixtures connecting fiber-optic illuminators to LED sources allow “long lamp life and a small illuminator footprint.” In some LED-fiber-optic hybrid systems, each optical head has its own LED source, allowing for greater individual control and enhanced dynamic displays.
Discussions sparked by a 2010 letter written by Dale Kronkright, head of conservation at the Georgia O'Keeffe Museum in Santa Fe, N.M., cautioning the display of light-sensitive materials under LEDs have also subsided, and for good reason, says Jim Druzik, senior scientist at Los Angeles's Getty Conservation Institute (GCI). The warnings were based on studies of narrow-band LEDs, a technology that was virtually replaced by white LEDs within about a year. “The initial concern is no longer relevant,” he says. Manufacturers have balanced out the high blue peaks in early LEDs' spectral power-distribution curves, which have the potential to fade yellow-colored dyes. As director of the Museum Lighting Research Project at the GCI, Druzik found no significant differences between the fading effects for 15 dyes on silk or paper caused by exposure to two white LEDs or a tungsten halogen lamp.