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Y. Magnusson, Museum Lighting & LED Technology, e-conservation Journal 2, 2014, pp. 34-42
Available online 26 May 2014
doi: 10.18236/econs2.201408

Museum Lighting & LED Technology

Review by Yngve Magnusson

April 18-20, 2014
Copenhagen, Denmark

Organised by
Department of Photonics Engineering, Danish Technical University

This review is for institutions and individuals that are planning, or are in the process, of changing parts or the entire museum lightning to LED. The main text present the event held in Copenhagen, mainly for Scandinavian Museums, but also highly relevant for institutions worldwide that are looking for good alternatives to the main actors on the market for museum lighting. The presentations and case studies stretched from the planning work of the architect, and insecurity from the trustees in the museums as well as the scientific covering of the subject. The references at the end of the review can also be used by institutions which not participated at the conference. The main purpose of the conference can be said to show how to approach LED with an open attitude and discover how to use the new possibilities which are offered with this young light source. If there are insecurity about which color temperature and color rendering to choose for your next project can it also be interesting reading.

It was around 30 years ago that LED became more common in art installations, a good reason for conservators to learn more about the use of this technology. For many years, LED has also been an important topic when it comes to saving energy. In the beginning the technique was expensive and the payback period was, in many cases, so long that it was not possible for institutions to change. Hence, the current strategy was to postpone the adoption for later. In 2009, when the clear incandescent light bulb was phased out in the European Union, the discussion about LED in museums resurfaced. The producers of museum lightning also became more active at this time. An early discussion of this technology had caused an insecurity concerning the use of LED in museums because of a large part of harmful wavelengths. The development of LED continued and UV and IR radiation was removed from the light sources recommended for museums. Nevertheless, the concerns of harmful wavelengths are still persisting. During this time it became clear that it is possible to make LEDs that are suitable as light sources in museums, reaching the high standards of curators and conservators, without having to make big investments and have to change the complete lightning system. “Retrofit”, or keeping the old light fittings and changing only the light source, became a term often used when discussing light.

With time, the price kept dropping, and we are now aware that there are “good” and “bad” LEDs. The new issue is, then, how do we recognize the “good” LEDs? This conference covered the subject of “light quality” with the discussion of “Solid State Light” (SSL), meaning the light source, color rendering index (CRI), correlated color temperature (CCT) and light output (Lumen/Watt). It was also shown how UV and IR radiation have been removed and that it is possible to reduce the most harmful wavelengths, and even to almost eliminate them. The possible drawbacks by doing this were also discussed. The more obviously advantages with LED, the dimming properties and enormous life span, also by heavy use, are now common knowledge and was less discussed. The recommendation of CCT deviated between the presentation, and it was also one of the issues which the conference organizers gave to the audience. Do we need other recommendation for CCT in Scandinavia?

The payback period has also been significantly reduced. The conference showed examples from two up to six years of use before the investment is paid of. In some cases, under certain circumstances such as retrofitting, a payback period of six months can be reached!

All presentations can be downloaded from the conference website.

The Presentations

The latest of Scandinavian conferences that cover the topic of LEDs was held in Copenhagen during 18th-20th of April this year. The conference “Museum Lighting and LED Technology” was organised by the unbiased Department of Photonics Engineering at the Danish Technical University (DTU) which has been evaluating the development of LED for several years, but also has taken active part in developing LED technology specifically for museums. During the conference, participants were offered practical demonstrations and theoretical background as well as a workshop to tie up the questions from the participants at the end of the event. Several professions connected to light in museums got the opportunity to share their experiences with LEDs.

The conference started with the presentation of the meeting’s main topic, to share the knowledge obtained by DTU in their research with LED. Scientific views and experiences by other institutions were also presented. Different case studies from different countries and continents showed the possibilities LED offers, both in scientific and amusing ways.

In my opinion, the most important, with the highest impact and relevant contributions to the conference, were the two first presentations. Dr. Carsten Dam-Hansen, senior researcher at DTU Photonic presented the fundaments of light in an understandable way. The red line was the development of a LED for the treasury at the Royal Danish Castle. In this project, DTU and its partners developed a LED which gives a CRI > 93 by CCT 2200-2400 K. This LED gives a better visitor experience, and protects the objects from damaging radiation. Dr. Dam-Hansen finished his presentation to stress the importance of always test the light sources for: spectral power distribution; luminous flux; efficiency; CCT; CRI; luminous flux and color maintenance; intensity distribution; and illuminance and irradiance. This final recommendation is in my opinion the essence of how to proceed when converting to LED. I would also recommend following the work of Dr. Dam-Hansen on developing international test standards for LED light.
The next speaker was Mr. Jacob Munkgaard Andersen from CSO of DOLL, one of eight so-called Green labs that the Danish government supports for a rapid implementation of energy efficient technology. The Danish Green Labs work on testing and demonstration of energy savings in close cooperation between research institutes and private companies. Museums can also use these facilities for testing light which is, in my experience, unique in the world. In practice, a museum can send the lamps (retrofits) to DOLL’s Quality Lab to test their usability and obtain the values of the criteria that Dr. Dam-Hansen listed previously. This service is supported by the  Danish government with 40% of the actual costs. Mr. Munkgaard Andersen stated that museums in other countries can also use this service. Mr. Yngve Magnusson from KODE, in Bergen, Norway showed in his presentation that KODE has used the data delivered by DTU Photonik, which are identical with the services from DOLL, for the planning of two LED projects where savings between 50% and 80% were reached by retrofitting instead of changing the complete lighting system. In the future KODE will use the services of DOLL.

Dr. János Schanda, Professor Emeritus at the University of Pannonia, Hungary where he taught colorimetric and visual ergonomics, gave an   excellent presentation of choosing LED spectrum for frescos giving the example of the Sistine Chapel. Dr. Schanda promoted a CCT of 3000-3500 K as “warm white”, where Dr. Dam-Hansen used CCT 2200-2400 K as “warm white”. The difference in CCT was announced with a question mark in the invitation to the conference: does Scandinavian museum needs another light than Museums in other parts of the world? Is a higher CCT required in the Mediterranean region? This question was also indirectly asked on the field trip that took place the evening before the conference. The participants were put on test by Giancarlo Castoldi, Director of Targetti Poulsen, Italy in an experiment where seven different light sources and technologies were evaluated by the participants. The result will later be presented on the homepage of the conference. Dr. Schanda contributed in many ways to the conference through illustrative answers of questions and contribution to the workshop. His long experience of the work of CIE could have added an extra dimension to this conference if only one extra day could have been added.

For the conservators in the audience, the contribution from Bent Eshøj, from the Danish School of Conservation, was not new but was still very informative. Mr Eshøj has worked with light in museums for two decades and is well oriented in the issues concerning the employees responsible for the museum objects safe keeping and the  dilemma of “saving” vs. “showing”. Bent Eshøj not only converted the information presented in the first presentation to the language of conservators, but also prepared the audience for the later presentations by putting LED in the context of conservation. What might contribute to confusion about the LED properties is the graphs of “damaging ratio”, “relative photon energy” and “relative sensitivity” used in several presentations, not only by Bent Eshøj, but also avoided  by others. In my opinion should we wait to use it until we have some kind of standard to rely on?  I will not use it again until then.

Four contributions to the conference were mainly case studies: Giulio Antonutto, Light designer from ARUP, London; Johan Carlsson, Creative Director, JAC Studios, Stockholm; Eric Hagan, Conservation Scientist from the Canadian Conservation Institute, Ottawa; and Yngve Magnusson, Head of Conservation, KODE, Bergen. The two first combined their case studies with a philosophical view of light and its use. Mr. Antonutto also contributed with plenty information about light and the issues of choosing light. As a light designer it may be his normal activity although I’m afraid that for the audience there was, in my opinion, too much information and too fast in the time frame of 40 minutes. In the future, I would like to hear a day lecture of Mr. Antonutto. The presentation of Mr. Carlsson was focused on the exhibitions he has supervised in Denmark and Sweden. He did not go deeper into the technique of LED.

Both Dr. Hagan and Mr. Magnusson showed case studies tied to changing light in a museum. Dr. Hagan’s case is located in Yellowknife, Canada, which is approximately equivalent in terms of daylight hours per year with mid-Sweden. This makes his presentation relevant for the participants, even if Yellowknife is far from Europe. The presentation from Dr. Hagan showed the practical considerations as well as the theory in the decision project. The information given can also very well be used in Scandinavian settings, and I consider the presentation very relevant for the audience, although it did not presented so much direct hands-on information as the contribution from Dr. Dam-Hansen. The presentation from Dr. Hagan can very well be used to argue for the benefits of retrofitting the museum instead of changing the whole light system. The same can be said for the last of the case studies presentations. Mr. Yngve Magnusson used the criteria of Garry Thomson, as published in 1986, to show that they are still valid in the process of planning light for exhibitions. These contributions went further to show the new possibilities that LED technology offers to protect the objects and to save energy. The term “visitor controlled lightning” was used to show the work of KODE to reduce the exposure (in lxhrs) for objects. The average exposure in the galleries with LED is today ca. 50% less than the limits recommended by ICOM. Also, the energy consumption is reduced to 95% with the use of dimmable LED connected to a system of sensors and controllers, which are systems available today even for private households.

The two most eye-catching presentations were done by Mr Giancarlo Castoldi, director of Targetti Poulsen, Florence and Dr. Marc Fontoynont, Professor of Lightning Technology and Design in Aarhus. Mr. Castoldi’s presentation was both funny and serious, the most interesting part being his work with designing light for the Exhibition “The Greek from Toledo”. Mr. Castoldi has contributed with the light to this exhibition and the examples shown in the presentation were very convincing for the high pay-off connected to focus on the light for the art. The same as DTU and Dr. Dam-Hansen’s team has done with increasing the visitor experience at the Danish Royal Treasure has been done with El Greco’s paintings by Mr. Castoldi. While the first is a permanent exhibition, the later can only be seen until 14 of June, 2014. I recommend the readers of this review to go to the homepage of the conference and look through Mr. Castoldi’s presentation since it contains many good examples of how to use light to give the most   to the visitors, in terms of contrast use.

Mr. Fontoynont's presentation gave a very good insight in the planning process for museum lighting. One would wish that more museums applied this kind of professionalism. The presentation contained plenty information for institutions that are planning to change to LED, although the work presented is not for the institutions to do themselves. Professionals, like Mr. Fontoynont will always be required in seriously lighting projects. The final conclusion from Mr. Fontoynont also showed a degree of integrity in recommending light for museums. His conclusion to use “volume lighting behind diffusing glazing” is, in my opinion, the best way to light galleries and also the most economical one. The use of “visitor controlled light” can improve the experience. In the presentation of designing a new LED for Mona Lisa in the Louvre I reacted on the specification to use a CCT of 3200 K. This is higher than the recommendation from Dr. Dam-Hansen (2200-2400 K.) and the average of what Dr Schanda recommended as warm white (3000-3500 K.). Copenhagen’s latitude position, where Dr.Dam-Hansen works, is 55°41'N while Paris is located on 48°51'N and Rome is 41°54'N. The question from the conference organizers to the participants seems to be valid: do we need another CCT in Scandinavia than the rest of Europe? Of course the result would also be applicable to many other regions on the same latitude. If we planned an imaginary exhibition in the Norwegian city of Honningsvåg, one of the most northern cities on the European mainland positioned at latitude 70°59'N, would we, according to what the presentations showed us, go lower than 2200 K? This is, in my opinion a valid question for DTU to continue researching.

The last contribution was made by Nigel Sylvester from ERCO Lightning, London the only commercial one. This was the first presentation that showed the participants how a LED illumination is actually built. This was done in an understandable and non-technical way. His presentation also explained the energy savings context in the UK and the collaboration with well-known Galleries in several countries. This presentation was the only one indicating that a high CRI is not essential to museum lightning, citing a Swedish gallery where a CRI of 80+ was the wish from the gallery director. ERCO also goes another way than those recommended by Dr. Dam-Hansen and Dr Schanda. ERCO offers two different CCT for LED: 3000K / CRI 90+ and 4000K/ CRI 80. The later has a higher light output (125 lumen/W), almost 30% more than the first (90 lumen/W). This means that galleries with long distance between lamp fittings and objects will always have to stay with the lower CRI. The future will show if ERCO can keep up this policy.

From left to right:
Conference participants.

Intervention of Dr. János Schanda, Professor Emeritus, University of Pannonia.
Giancarlo Castoldi, director of Targetti Poulsen, during his presentation.
All photos by Anders Thorseth.

The Day after the Conference - The Workshop

Almost half the participants chose to stay for the workshop which was held the consecutive day on the same location. The workshop was   intended to clarify the demand for a guide or similar tool for the selection of LED for museums in the regional context of northern Europe. The goal was to identify challenges for lighting that are more pronounced or specific for Scandinavia. During the presentation there were some challenges that were presented: opening hours beyond the normal daylight period during a long time of the year, high cost of energy and special preferences for CCT among the population mentioned. The organizers also wanted to summarize the state-of-the-art within museum lighting guidance.
Yngve Magnusson opened up the day with a short introduction before Dr Hagan continued introducing the “Guidelines for selecting Solid State Lighting for Museums” a joint project between the Getty Conservation Institute (GCI) and the Canadian Conservation Institute (CCI). The guideline is already known by museum professionals since 2011 but Dr Hagan provided further and more detailed information that is valuable for museums such as how can the criteria of other organizations like “Energy Star”, “Gateway” and “Lighting Facts” be useful for institutions that are planning lighting systems. After this presentation, the participants should know how to find out more about third-party testing and certification of LED products. The presentation is also available on the conference homepage.

Afterwards, Dr. János Schanda picked up the thread and gave two small presentations to clarify some issues and to show us more about color rendering in the internet.

Before the participants got active in the workshop tasks, Mr Hanz Nyström spoke about the ongoing process of a European standard for museum lighting. He could only talk in general terms about this project due to the ongoing process. The standard will be published later in 2014.

The workshop was managed by Mr Jesper Wolff, from DTU Photonic. The first workshop task was to point out and to prioritize the most urging issues for museum professionals in the transition to LED lighting with regards to conservation, technical aspects, aesthetics and economics.

The work was performed in groups and presented verbally by each group. A short summary was that the participants wish to learn more about “bad” and “good” LED to be sure that they are not harmful for the objects. The technical understanding needs to be improved in order to know that the right choices are taken. The aesthetics is an issue, but not one that needs much guiding. The economy is of concern, mostly in case of how to finance and calculate the transition to LED. The result from the workshop will later be presented on the conference homepage.

The second workshop task was to identify the best possible tool to facilitate the transition in museums in the areas mentioned in previous task. The groups seemed to agree on that it should be a web-based solution, but if it should be an interactive system, like social media or a passive tool to calculate costs, etc., was not clear. Both seem to have its supporter. The groups in favour of social media meant that it must be a closed forum so it can stay focused on the subject. It was proposed that the people from the conference should be able to stay in touch after the workshop and so a closed discussion group in LinkedIn was proposed. Another proposed tool was a procurement tool for museum to avoid mistakes in the process of buying LED through a bidding process, something that is mandatory if the project is big enough.

The workshop finished with a discussion round, and the participants wished to stay in contact for further arrangement to continue to discuss lighting.

From left to right:
During the field trip to Thorwaldsen Museum.
Field trip at Tøjhus Museum.
Poul Kattler addressing the audience during the field trip to the Experimentarium City.
All photos by Anders Thorseth.

The evening before the Conference: The Field Trip

The first part of the conference consisted of a field trip to institutions in Copenhagen that have been using LED in new and old presentations. The key employees spoke about their experiences and the challenges with the LED lighting and what concerns they have had in the change to LED.

At the first institution, The Tøjhus Museum, lighting designers Jørgen Kjer and Johan Carlsson presented the new installed permanent exhibition. It was outspoken that the project’s economy directed the fitting and light source choices. The main emphasize was not on a high CRI or an awareness  of color temperature but an innovative use of retrofit and standard fittings.

William Gelius, curator at the Thorvaldsen Museum, showed us the ongoing process of changing to LED. Being a museum built for daylight, the Museum had the challenge to install a new lighting system without drilling new holes in the walls. The participants got an idea of how important it is to consider the positions of the light sources to avoid disturbing glare and strong contrasts. The museum is in the process to achieve great energy savings but must still work on the placement of the light sources. In 3-4 months the visitors of the Thorwaldsen Museum will get a better impression of how the light will work!

In the trip to the third stop, Poul Kattler from Experimentarium City, not a museum but a science center, presented the institution and explained his experience using a track mounted LED system from ERCO. Mr Kattler did not hide away that they are a private financed science center, not depending on public financing. One main reason for choosing a track system was the flexibility and adaptability in changing exhibitions. He also stressed the usability of the three phase system: one phase for common lightning, other for the direct spots, and the third for running the installations.

At the National Gallery of Denmark (SMK), Jørgen Wadum and Niels Borring did not show so much about LED but explained more in detail why they have waited so long to start using LED at the museum, a project that is still undergoing. The actual demonstration at SMK was conducted by DTU, showing their new test boxes and references for testing light sources. Giancarlo Castoldi, together with DTU, tested the participants by conducting a survey on how they responded on seven different light sources on similar art pieces. The result will later be presented on the conference homepage.

To finish, some interesting statistics:
• In total, there were 124 participants, from which 90 men and 34 women, from 11 countries;
• There were no female presentations;
• Denmark, Sweden and Norway were best represented.

If one had worked with light in museums 30 years ago, one had to be concerned about testing the UV and IR filters that was required to obtain a suitable museum light. CRI was known but not considered to be a big issue. It was possible to get light sources with CRI higher than 96 as they were already in use in industry. However, since the price for purchasing and maintaining the lights were too high for the museums, they settled with CRI 80. Nevertheless, already in 1978, in the first issue of Museums Environment, Garry Thomson recommended to use CRI >90!

Back then, the UV filters that were tested almost never fulfilled what the manufacturer’s fact sheet said: 99% absorption of UV showed to be 70% at the very best. We had to keep on testing until we found something that worked. And the next time someone would buy the same filter it had to be tested again. This was the work done by museums professionals around the world.

Today, the light sources (LED) are free from UV and IR radiation. The damaging wavelengths in the blue and green fields are also treated more seriously. Thirty years ago most museum professionals did not know how they could be controlled.
The recommendation of CCT 30 years ago spanned from 3500 K. to 6500 K., depending on literature, but also from which country it was being discussed. Back then, this was also connected to the photographer’s work since different films where calibrated to different light sources. Much has changed in the last 30 years but some things remain the same.

The conference shows that we still need to test our light although nowadays we can get the light that we wish for without external filters. We can get a higher CRI if we think that we need it or if it improves the visitor experience. The conference in Copenhagen also showed that we should start thinking seriously about the CCT of our light source, and to adapt it to where we live.

Yngve Magnusson