049
GRAND NATIONALS
Both the National Gallery and the National Portrait Gallery in London have, after intensive investigation, arrived at the same conclusion: ERCO’s LED lighting is the future for them.
Above and left National Gallery. Far left National Portrait Gallery.
With or without UV protection filters, low- voltage halogen lamps have a higher relative damage factor than warm white LEDs. For both preservation and energy efficiency reasons, it is therefore recommended to use warm white LEDs to illuminate sensitive objects. Daylight white LEDs are unsuitable for lighting in museums due to both their poor colour rendition and their higher relative damage factor.
Working at 5 metres, museum technician Tim Knight is, once again, in Room 14 of the National Portrait Gallery aiming one of the ERCO Optec LED spotlights that illuminate 18th century portraits from the heyday of the British Empire. This will presumably be the last maintenance for quite a while though. With the introduction of long-life LED technology, regular lamp replacement and the associated danger of disturbing a lighting arrangement, are set to become problems of the past. The LED’s longevity, the related reduc- tion of maintenance costs and the reduced risk of damaging priceless exhibits when manoeuvring ladders and platforms are important arguments for new lighting tech- nology for museum and gallery operatives like Tim Knight and his colleagues. However, the focus of discussions currently ongoing in museums and galleries around the world is regarding three further questions. How much energy can LED lighting save, is the lighting quality equivalent and, above all, how do LEDs fair in terms of the preserva- tion of exhibits? The museum and gallery community is waiting with baited breath to see how the large and famous establish- ments, that have the relevant technical, curatorial and preservation expertise, are answering these questions. Two top London institutions that are steeped in tradition, the National Gallery on Trafalgar Square and the nearby National Portrait Gallery, are now making steps toward the future and are converting their galleries one by one to LED light.
Overleaf mondo*arc editor, Paul James chairs a discussion panel consisting of key staff at the National and National Portrait Galleries as well as the ERCO team.
Findings gleaned by experts at both galler- ies while in the course of their investiga- tions and product samplings of LED technol- ogy, ultimately leading to the decision to specify ERCO’s LED lighting tools, are also of the highest interest to other museums and art galleries. The bar for measuring LED lighting quality was already set high since the existing systems were mainly from ERCO and, at the time of their planning, were state-of-the-art. They included com- puter-controlled regulation of daylight and artificial light, plus spotlights for low-volt-
age halogen lamps fitted with UV filters and occasionally with colour correction filters to bring the warm-hued light of incandes- cent lamps into line with daylight. In terms of energy-saving potential, the figures returned by the National Portrait Gallery are very clear and concise. Since changing to LEDs, the lighting of the galleries now consumes 68% less electricity and that’s without the inclusion of savings made by a reduced thermal load on the air-condition- ing. The issue of exhibit preservation can also be addressed because the light irradiation load on the artworks can be quantified using the respective spectral constitution of the light source. To sum up: while daylight white LED spotlights are not to be recommended for sensitive exhibits due to their stronger peak in the short-wave blue spectrum, the over- all load of warm white LED spotlights is less than that of low-voltage halogen spotlights. A big advantage of LEDs in this respect is that their light is inherently free of the in- frared and ultraviolet components that are so undesirable in a museum or art gallery. Halogen spotlights, however, require the appropriate filters and these always reduce the efficiency of a luminaire.
But what about the lighting quality that, af- ter all, can only be measured subjectively? Experts agree that, yes LED light has a dif- ferent effect, but in many respects it is ac- tually even better than that of its predeces- sor. The light of warm white LEDs, which is slightly cooler in colour than halogen light, is perceived positively as both brighter and fresher, allowing slightly lower illuminances. For the same reason, LED light also mixes favourably with daylight. Red and gold hues are no longer over-emphasised and overall this kind of colour rendition is well suited for most exhibits. Well, that’s what the experts say, but what about the visitors? “We braced ourselves for the reactions, but nothing came! There were no complaints at all,” states Allan Tyrrell, Chief Engineer of the National Portrait Gallery, adding, “be- lieve you me, the visitors do complain about just about everything else.”
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