Since it is well established that light-sensitive materials - typically illustrated by Japanese wood block prints, dyed textiles, watercolors, pastels, color photographic images, biological specimens etc - are damaged ( ie undergo color shift such as loss of coloration – fading -, darkening, yellowing or color-shift) by radiant energy WITHIN the human visible spectrum, any light-sensitive material whose damage spectra (within the absorption spectra as opposed to the reflection spectra) contains any of these isolated LED output peaks would undergo damage at 20% to 400% faster rates than if lit at the same light levels with an unfiltered MR 16.
To this information, Jim Druzik, Senior Scientist with the Getty Conservation Institute and project leader for the joint O’Keeffe Museum – GCI – University of Texas El Paso light damage prevention project adds:
“It has been demonstrated that some LED mixtures will accelerate damage more rapidly on natural yellow dyes. The SPD is useful for calculating gamut area mapping and CRI - so between those two metrics one can determine color rendering. But there are no damage-activation spectra of most dyes and pigments. Because so much is piled on to narrow bands in LEDs, the possibility of hole burning is very possible and trying to be "green" with so little knowledge is Russian Roulette and the LED green committee is playing with fire. At this time I don't think LEDs are ready for prime time both from the point of view of color rendering and conservation. Clearly two LEDs with a bridging phosphor is better than all LEDs but some manufacturers have driver problems, green is mismatched for optimal color rendering, and only one manufacturer hits the Energy Star specification. I know all this because I just came back from NIST which is a hotbed of research on LED lighting and that's most of what all the current research is about. The one Energy Star qualifier does achieve an amazing 65 lumens/Watt but I didn't see it turned on so I don't know how good its color is. As you know, it could be any CCT yet if displaced off the spectrum locus for blackbody illuminants, it'll still could be a disaster. I have it on my "To Do List" to buy a few of the Energy Star qualifiers and measure their spectrum. I just got a piece of NIST software which will display two sets of Munsell swatches according to their appearance side-by-side with a reference illuminant. That might be the way to go first.”
We hope this clarifies the need for using extreme caution when considering LEDs for the illumination of light sensitive materials. To reiterate our earlier point, for non-light-sensitive materials where the color discrimination of the object is not critical to its appreciation and understanding and in offices and non-collection areas LED’s present a low-energy-of-operation alternative. For light sensitive museum materials, there is no existing data that demonstrates that they are either safe or effective at the 50 to 70 lux levels commonly used to extend the life of these materials during exhibition.
In addition to the original post Mr. Kronkright adds:
It is important to grasp the fundamental fact that 50 lux, 65 lux or any light level from an LED source is NOT the same as 50 lux, 65 lux, etc. from an incandescent source. The spectral power distributions are different. Guidelines for lighting light-sensitive museum materials are based upon the spectral power distribution of most halogen-incandescent sources (e.g. MR-16, Par 38 lamps) and their fading behaviors with materials of known sensitivities, the ISO Blue Wool Standards. Since light sensitive materials generally fade first as a result of exposure to the visible light spectrum, and since most museums are aware of the need to filter for UV and IR radiation, the fading and color-shifting behaviors of light sensitive materials may be significantly accelerated as a result of absorption of the elevated narrow energy bands within the visible spectrum delivered by LED sources.
I will be reviewing the latest Federally confirmed data at the DOE Energy Efficiency and Renewable Energy testing laboratory and the Committee of Illuminating Engineering Society of North America, author of the RP-30 recommended practice for Lighting Museum and Art Galleries, over the next two weeks. We may find that there are sources that do less damage to light sensitive materials than the 2007 lamp data I site in my posting. If so, I will update the AIC-Green Task force, the PACIN listserv and the RCAAM listserv and post a link to any DOE-EERE-IES joint statement to museums.
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