Usually when we talk about lighting on the blog, we talk about the domestic and commercial applications. But today we'd like to talk about museum lighting and what it can teach the rest of us.
Lighting has a role in directing focus: subtly guiding audiences and customers around a space. We've touched on this before in relation to the retail sector.
Looking into the considerations that go into the lighting of exhibitions also reveals the damaging effects that light can have.
Besides, we live in London, a city that boasts 50 museums per square metre in the centre. We love museums.
Directing Focus
Using spotlights in an exhibition area can highlight specific objects and guide visitors towards certain areas, often in sequence.Varying the levels of light in this way can encourage visitors to spend more time with brightly-lit items while ensuring that the the circulation spaces visible, but remain subtle.
The problem inherent in this approach, however, is that exhibitions tend to change every few months, so the spotlights need to be adjustable.
A track system is one solution, allowing lighting designers and curators to adjust the levels at spots along the track, but the track itself may need to be re-installed depending on the size of the overhaul.
Aside from placing considerations, there is also the need to reduce glare, particularly where display cases are used.
General wisdom suggests a suitably angled incidence of light (about 30°), but in reality the lighting designers, architects and curators need to work closely to combat the issue.
Colour rendering (which probably warrants a blog post of its own) is also a problem to overcome.
Briefly: a high colour rendering index (CRI) is required to display the 'true' colours of a display item.
Minimising Lighting Damage
Those items on display are often quite old, or at least quite sensitive.While such items are often kept in display cases or behind protective barriers (usually glass or clear plastic), what the public often don't realise is that the light can actually damage such items.
When a surface is exposed to light energy (photons), that surface either reflects or absorbs the energy. Our eyes pick up that reflected energy, which is then absorbed.
The energy that is absorbed causes chemical reactions - which lead to structural changes such as embrittlement (known as photomechanical damage) and photochemical damage, chiefly causing pigment loss and colour fading.
Book collectors will recognise this as 'sun-bleaching'; books left in direct sunlight for too long will become strangely coloured from photochemical damage.
It gets much worse over time, and since museum pieces tend to be on display for several hours a day, for months, accumulated photochemical damage can severely damage the item.
It was previously thought that UV rays dealt this damage alone, but more recent research shows that even visible light causes photochemical damage.
That's not to mention the radiant heat from light sources, which can cause further degradation - particularly of paint, bindings - and the structural stress caused by alternate heating and cooling as the luminaires are turned on and off over time.
The ideal lighting setup maximises visibility while also minimising the amount of light and heat energy an object absorbs. Leading designers are proposing LED lighting as a solution to this problem.
After all, LEDs carry a minimal thermal load and emit very little heat
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Although this solution does not completely cut out the problem of photochemical and photomechanical damage, the light output of LEDs are on just the right wavelengths to minimise the risks associated with continual lighting.
In Conclusion - Use LED Spotlights!
This is only a very basic introduction to the lighting considerations of museums and for general display purposes.The two problems covered in this post - the need to be able to adjust lighting and to minimise the risks of photochemical damage - can actually be solved by one of our products: the Illuma LED Shaker track spotlight.
We actually talked about this product in our post on retail lighting design, and we mentioned how easy the Shaker is adjusted as well as its excellent colour-rendering abilities.
If you're interested, the Illuma LED Shaker is available in our online store - or feel free to come to our showroom and ask one of our experts!
