# Art/Object Issues > Lighting >  LED as a light source for sensitive objects

## T. Ashley McGrew

Here is a recent post sent out on the Registrars Committee listserve as a result of strong interest in discussions on the PACIN listserv on this very current topic (this is one of two parts) :



Hello Museum folk,

With the strong emphasis on "green" technology these days there has been a movement towards the use of LED lighting in cases and galleries. 
As part of a recent discussion on this topic on the PACIN listserv a post by Dale Kronkright - head of conservation for the O'Keefe Museum and including a quote from Jim Druzik of the Getty Conservation Institute struck an alarming cord. With both individuals permission I would like to pass that post on to Museum-L folks. 
Those of you who are also on the RCAAM listserv may have seen it - if so my apologies for the repetition. 

Obviously there are previous posts about poor CRI ratings typical of LED and the important distinction between Color Temperature and Color Rendering (in the form of a light sources CRI - Color Rendering Index) that are not included here.

For people whose jobs include the responsibility for making informed decisions concerning the safe handling, packing, crating, installation, and storage of cultural materials I would recommend taking advantage of the PACIN (Packing, Art handling, and Crating Information Network) website and listserv as a resource.
Anyone interested can either join the listserv themselves or simply request that those individuals who are the hands-on preventive conservation practitioners within their institutions do so.

Here is the post and some additional comments provided by Dale Kronkright:

++++++++++++++++++++++++++++++++++++++++++++++++++  +++++++++++++++++++++++++++++++ 

*From:* Dale Kronkright <conservator@okeeffemuseum.org> [Add to Address Book] 
*To:* pacinlist@pacin.org 
*Subject:* Extreme caution urged when considering LED's for illumination of light-sensitive materials
*Date:* Mar 24, 2010 8:46 AM
*Attachments:* Hole burning potential of LEDs.pdf unknown-135 B 


Below is a letter sent to the Green Task Force of the American Institute for Conservation of Artistic and Historic Works, at their request, clarifying the potential problems of using LEDs to illuminate art cultural heritage materials. Members of the task force suggested we also post this email to the PACIN list serve. First let me say that LEDs present a low-energy-of-operation alternative for the illumination of non-light-sensitive museum materials where the color discrimination of the object is not critical to its appreciation or understanding and in offices and non-collection areas.

I believe the existing reported data demonstrates that LEDs are a potentially damaging light source for light-sensitive museum materials and are deficient where accurate color discrimination within the human visible spectrum is required. The deficiencies of LED light sources, both for color rendering and for their narrow emission spectra, is not new information. The CIE data first explaining these deficiencies in detail was published in 2004. I believe the manufacturers are acutely aware of these deficiencies. Jim Druzik of the Getty Conservation Institute has just returned from an NIST meeting where the efforts of the manufacturers to overcome them was frequently discussed. Unless conservators ask very pointed and direct questions, my sense is that manufacturers have not initiated discussions that reveal the risks of LED light sources to light sensitive materials.

The color rendering indexes of these light sources, when tested in independent studies, has been near 60% at best across the entire human visible spectrum. Experimenters have documented considerable human impairment with color discrimination with materials viewed under both 2-phosphor white LEDs and RGBA and RGB 4- and 3- source white LED sources. If exposing light-sensitive materials to damage within exhibitions is to severely limited, then certainly the few times they are exhibited ought to be done so that people can accurately discriminate between the colors we are so carefully trying to preserve. To expose them to damage AND prevent an accurate sense of their visual characteristics seems to be the biggest crime of all.

I will attach copies of 2006 un-filtered MR-16 halogen incandescent lamp, a 2-phosphor white LED, a red, green, blue, amber white appearing LED and a red, green, blue white appearing LED, each taken off a standard spectralon tile at 660 lux. Each of the SPDs has a heavy horizontal line at 0.01W·m−2·nm−1 , the highest power output of a broad, continuous incandescent lamp. Please note that the power of the narrow wave peaks produced by the LEDs is 20% to 400% higher than the halogen MR-16 at the same light level.

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## T. Ashley McGrew

Part two of post:
 
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.


*Dale Kronkright*
*Head of Conservation*

*Georgia**O'K**eeffe Museum*

*dkronkright@okeeffemuseum.org*
*505.946.1041 tel 505.946.1093 fax*
*217 Johnson Street Santa Fe, New Mexico 87501*
*USA*




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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## mike hascall

Wow. And I thought LED was the future of all lighting. Thanks

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## Kurt Christian

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:

    <URL:http://www.nist.gov/physlab/div844/grp05/vision_color.cfm>

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

    <URL:http://www1.eere.energy.gov/buildings/ssl/test_labs.html>

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

    <URL:http://www.ssl.energy.gov>

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).

    CALiPER Program
    <URL:http://www1.eere.energy.gov/buildings/ssl/caliper.html>

    CALiPER's Searchable Database
    <URL:http://www1.eere.energy.gov/buildings/ssl/search.html>

    CALiPER Benchmark Reports:
    <URL:http://www1.eere.energy.gov/buildings/ssl/benchmark.html>

    In particular:

    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>

    Color Rendering Index and LEDs
    <URL:http://www1.eere.energy.gov/buildings/ssl/cri_leds.html>

    Color Quality of White LEDs
    <URL:http://www1.eere.energy.gov/
        buildings/ssl/color_quality.html>

    LED Lifetimes:

    <URL:http://www1.eere.energy.gov/buildings/ssl/lifetime.html>

    <URL:http://apps1.eere.energy.gov/
        buildings/publications/pdfs/ssl/lifetime_white_leds.pdf>

    LED Luminaire Reliability
    <URL:http://apps1.eere.energy.gov/
        buildings/publications/pdfs/
        ssl/Luminaire_Reliability.pdf>

    Understanding Photometric Reports for SSL Products
    <URL:http://apps1.eere.energy.gov/
        buildings/publications/pdfs/ssl/
        understanding_photometric_reports.pdf>

    Energy Star Criteria for SSL
    <URL:http://www.energystar.gov/
        ia/partners/product_specs/program_reqs/SSL_prog_req_V1.1.pdf>

    DOE GATEWAY Demonstration Reports
    <URL:http://www1.eere.energy.gov/
        buildings/ssl/gatewaydemos_results.html>

    Next Generation Luminaires--Design competition winners
    <URL:http://www.ngldc.org/09/winners.stm>



    **** Moderator's comments: The above URLs have been wrapped for
    email. There should be no newlines.

Jim Druzik
Senior Scientist
The Getty Conservation Institute

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## benjamen13

There is a LED/Fiberoptic option available.

Benjamen Salata
Project Manager
Luxam Museum Lighting
12201 NW 35 Street
Suite 534
Telephone: (954) 755-7254
Toll Free: (888) 339-4815
Email: ben@luxam.com

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## Pop Alexandra

You should check out NDR Electric. They have a lot of LED solutions for all kinds of requirements.

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