Osram brings readers up-to-speed on the considerations when looking to use LEDs in museums.
Lighting solutions for museums present a special challenge because the artificial light has to be gentle enough to protect works of art from long-term damage. The lighting also has to display the exhibits in their authentic colours. LEDs are ideal for meeting these requirements and are therefore being used more and more for museum lighting.
Light and heat constitute the greatest potential threats to works of art. Professional LED lighting provides pleasant high-quality light that is gentle on materials so it perfectly meets the needs of museums. In contrast to natural daylight and thermal radiators, light emitting diodes produce low UV radiation and minimal infrared radiation. Other benefits include long lamp life, high energy efficiency and enormous flexibility because the light can be easily adapted to individual circumstances either optically or electronically.
For works of art to be viewed properly, a certain brightness is needed on the surface. Standard illuminance levels in museums are around 50 to 200 lux, depending on the exhibit. New LED technology enables the most sensitive objects to be illuminated with 70 lux and more, instead of 50, without suffering any damage. The light colour is also significant in a museum setting. At the illuminance levels that are usual in a museum, the preference is for warm white to neutral white light colours (2500 to 4000 Kelvin) because this is the type of light that visitors find most pleasant.
The lighting must also be such that the visitors are not disturbed by glare. Visible light sources or strong points of light in their field of view detract their attention and are considered highly annoying. Often, an effort is made to adjust the artificial light according to the time of day – from a reddish hue in the morning to bright daylight at midday and then another reddish hue in the evening. This requires the lighting systems to be equipped with supporting optics and intelligent electronics. Another important aspect of museum lighting is the value of the colour rendering index (CRI) because the colours of the exhibits should be displayed as naturally as possible.
A special challenge: light for the works of Michelangelo, Kandinsky and co
To mark the 150th anniversary of the Liberation Hall in Kelheim, Germany (top), the city’s Archaeological Museum presented 60 original construction plans by the architects Friedrich von Gärtner and Leo von Klenze. 70 LEDTOUCH Tracklight luminaires with high-power light emitting diodes from Osram Opto Semiconductors were installed to master the enormous challenge of lighting these graphic objects. They create a bright room without causing any damage to the precious exhibits. To avoid the high cost of installing a completely new system, the new Osram luminaires were incorporated directly in the museum's existing track system.
The Municipal Gallery in the Lenbachhaus in Munich contains works of art by famous painters such as Wassily Kandinsky. Based on specifications submitted by the Munich city authorities, engineers and scientists at Osram developed a modern lighting solution. Each room is decorated in a colour appropriate to the works of art, and the light colours can be set accordingly between 3000 and 6000 Kelvin. More than 170,000 light emitting diodes and an intelligent lighting control unit can produce almost 100 different colour and dimming nuances, changing from the warm white light of the morning glow to the cold white light of the midday sun. Dimming is completely flicker-free and the light has excellent colour rendering properties.
In the Sistine Chapel in Rome (above), Osram is installing an LED lighting system designed to illuminate the world-famous works of Michelangelo without causing any damage to the sensitive materials. The new installation will provide a much higher illuminance than before. Compared with the current system, it will also consume 60 percent less power. Around 7000 Osram Oslon SSL LEDs will be used.
Scientific calculations have been carried out so that the colour spectrum of the light emitting diodes is accurately adapted to suit the colour pigments in the works of art. The light will be precisely directed to create uniform illumination without blinding the visitors. To ensure that the light comes from the same direction as natural daylight, the luminaires are being installed out of sight underneath the windows on cornicing.