Functional information on LED lighting getting better

[T. Ashley McGrew]

This year there has been a lot of back and forth about potential hazards as well as the low aesthetic performance that appeared inherent to the use of LED as a light source for art objects.

These factors have been emphasized on this forum in an effort to balance the overwhelming rush to impliment this technology based soley in its energy saving or "green" characteristics (and of course related fiscal benifits to institutions).

This is a developing area and at this point we are having trouble getting information that can actually enable individuals to make informed choices in terms of what they can actually buy - now - that will be safe and effective for use in their museums.

Many of the disadvanges of early LEDs in terms of their CRI ratings (Color Rendering Index) have been addressed and corrected in some bulbs and the risks that have been discussed in some listserves including this one have been found to be unevenly distributed.

Put simply there do appear to be LED bulbs that pose a relatively low threat to art work and have a high CRI rating 90 + (with 100 percent being the best rating - apparently one bulb had a rating of 96).

Unfortunately what at this point has not been made clear is which product this is!


In a nutshell though it appears that "Low to intermediate color temperature white phosphor LEDs (2700°K-4000°K)" have been tested to be lower in risk than a filter halogen light source.

This would seem to be good news and the statement gives us something to work with if not a specific product to purchase at this time.

Though most of the links here can be found in other posts here already on this website the best single source of information seems to remain the following link -


http://www.conservation-us.org/index.cfm?fuseaction=Page.ViewPage&PageID=1212 (http://www.conservation-us.org/index.cfm?fuseaction=Page.ViewPage&PageID=1212)

A helpful overview of many recent discussions is provided by Steve Wientraub at this link -


http://www.conservation-us.org/_data/n_0001/resources/live/Response%20from%20Steve%20Weintraub.pdf (http://www.conservation-us.org/_data/n_0001/resources/live/Response%20from%20Steve%20Weintraub.pdf)

[JasonO]

Thanks again for a nice summary with supporting materials!

Jason

[T. Ashley McGrew]

Another useful document from Steven Weintraub is titled "Using Risk Assessment Tools to Evaluate the Use of LEDs for the Illumination of Light-Sensitive Collections" please find the link below.

http://www.apsnyc.com/LED%20for%20Art%20Applications_Steven%20Weintraub. pdf

[T. Ashley McGrew]

From the PACCIN listserve

"Preservation of Light Sensitive Materials"

From:"Rosenfeld, Scott"

“Generally avoid picking higher color temperature lamps for light sensitive materials as these as these LED’s have an unacceptably large peak in the ‘blue region’ of the spectrum.“ This is the take-away from the report that Dale Konkright mentioned, “Guidelines for Selecting Solid State Lighting for Museums” by Jim Druzik and Stephan W. Michalski (June 2011). The intention of this report was to champion the use of quality LED’s in museums, especially warm LED’s <3500K, not to slow their adoption.

The CIE report on Optical Damage (CIE 157:2004) is the internationally agreed upon standard for how to evaluate the damage factor and choose the right lighting source for a collection of materials. The same criteria is used to evaluate the spectrum of any lighting source: LED’s, incandescent, daylight, HID or fluorescent. There are three factors that determine the damage potential of any lighting source: the quantity of irradiance, the duration of exposure and the spectral composition.
The recent discussion on LED’s has focused on the spectral component. While museums need to get better at evaluating the spectrum of our sources; the most important detail is still limiting illuminance and the duration of exposure (the first two factors). For example the CIE report indicates that daylight at 6000K is twice as damaging as incandescent at 2850K. This doesn’t mean that museums shouldn’t use daylight on their oil paintings. It is important to remember, “We have to accept a certain amount of damage caused by the very act of display” (Thompson, 1986). Lighting standards are chosen for what humans need to appreciate artwork, although that quantity of light still causes damage. So while 150 lux of daylight may be twice as damaging as 150 lux incandescent, 150 lux is still the amount of light that we need to see an oil painting at an optimal level. Highly light sensitive materials need to be treated with more care and kept away from high Kelvin temperature sources like daylight (IESNA RP-30-96).
The best advice is standard museum practice: Evaluate collections as highly sensitive to light (50-75 lux) or low sensitive to light (200 lux) and then stick to those lighting levels and control the duration of exposure. In my opinion the best new lighting technology to both save energy and preserve light sensitive material is the occupancy sensor that dims the lighting when the objects are not being viewed. LED’s are also a wonderful new tool and I’ve started using retrofit lamps in my collection, thankfully with the Getty conservation lab’s blessing.
For more information: CCI has a wonderful website that provides information on the preservation of light sensitive materials at http://www.cci-icc.gc.ca/crc/articles/mcpm/chap08-eng.aspx. I am chairing an IESNA committee to revise RP-30; the current manual was written in 1996 but is still very informative. It can be purchased at http://webstore.ansi.org/RecordDetail.aspx?sku=ANSI%2FIESNA+RP-30-96. Lastly; AIC’s Green Resources page has extensive information on LED’s. http://www.conservation-us.org/index.cfm?fuseaction=Page.ViewPage&PageID=1212


Scott Rosenfeld, LC, IESNA
Smithsonian American Art Museum