Date: 22 Apr 2010 From: Jim Druzik <jdruzik [at] getty__edu> Subject: Caution urged when considering LED light sources for light-sensitive materials
Several points in recent museum lighting posting on solid-state lighting are inaccurate--the first being that LEDs have CRIs of 60 at best. While there are many sub-par LEDs in the market with poor color quality, some of the better white, phosphor-based LEDs have color rendering index (CRI) values over 90 with acceptable correlated color temperature (CCT). However, recent work by the National Institute of Science and Technology (NIST) has revealed flaws in the CRI metric which can result in understated color rendition for LED sources. For more information on their work, visit their website:
It is essential to recognize that all lighting, regardless of source type, can cause a sensitive object to deteriorate over time. Fading is just one color appearance change. Color relationships can be altered from darkening and shifts in hue. Further, damage can extend to substrates inducing embrittlement, crosslinking, and loss of other mechanical properties in paper, textiles, and many polymeric materials.
Museum lighting research is ongoing to determine the characteristics of the safest light source for sensitive objects. Unfortunately, there is only one study (by Ishii, Mie et al., published by the Illuminating Engineering Institute of Japan in 2008) that has evaluated LED lighting and its affect on dyed textiles. Apart from the Ishii study, there is a lack of test data on this issue, and the use of LED lighting on light-sensitive objects in museums begs for more research attention.
In addition to fundamental safety concerns, when a new technology is considered for energy savings and/or maintenance reasons, perceived brightness and quality must be at least equivalent to that of the currently used light source. We urge any organization currently using or interested in using LEDs to do some basic analysis of each LED product under consideration. In addition to visual evaluation of an LED product, ask LED manufacturers to provide credible, standardized IES LM-79 test reports from a qualified testing lab for every LED product under consideration. These reports should provide the spectral power distributions (SPDs) of the specific LED product, along with CCT, light output, power, CRI and luminous intensity distribution. LM-79 test reports are essential in determining whether a LED light product has characteristics similar to the lamp currently in use in your institutions. Qualified test labs can be found by visiting
An IES LM-80 test report showing lumen maintenance data for the LEDs used in the product should also be provided by the manufacturer; this information, along with an appropriately detailed warranty, can help ensure maintained output and color over the product's rated life. More information, including a variety of useful LED fact sheets, is available on the solid-state lighting website maintained by the U.S. Department of Energy at
LED technology is evolving rapidly, and new products are entering the market every day. Knowing how to choose quality lighting products takes some effort, and this fundamental knowledge should be assembled and shared. In the near future, the Research and Technical Studies group of the American Institute of Conservation will take up just how they may facilitate and provide such a shared environment.
The Department of Energy supports a program entitled the Commercially Available LED Product Evaluation and Reporting (CALiPER) program. This site has a wealth of information on it, not all of which is equally easy to locate. The following links will help in finding further information on solid-state lighting (SSL).
The most recent Round 9 Caliper report (long term testing/Reliability) <URL:http://apps1.eere.energy.gov/ buildings/publications/pdfs/ ssl/caliper_round-9_summary.pdf>
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