Holburne Museum may be the last Tungsten Halogen exhibition lighting project we do.

It is with some sadness that I locked off that last MR16 based spotlight on Friday. I had enjoyed a day of tweeking and refining the lighting in the Holburne museum, enjoying that unique relationship the exhibition lighting designer can form with the museum objects that we get to light. It is certainly not the last time I will set a Low Voltage TH fitting but this museum looks to be the last we do where these will form the majority of the exhibition lighting. The MR16 and Low voltage low wattage TH capsule hit the mainstream about a quarter of a century ago. The first decade saw many problems with the technology. An unfamiliarity with low voltage wiring and the use of transformers caused many electricians mistakes from wiring a 12V lamp direct to mains voltage with the resulting very bright and explosive short life of the lamp, to melting cables when the electrician equated low voltage with low power and ran bell wire from transformers to lamps it is amazing this did not result in more fires than it seems to have.

At the lighting designer’s end we were plagued with dichroic lamps emitting different colours of light a major challenge in a museum with different lamps lighting different objects side by side when the colour differences were oh so noticeable. It was a bit over 10 years before the beast was tamed and we could generally rely on consistency between lamps, however in the past decade, increasing numbers of very poor quality cheap lamps have arrived from the far east necessitating arguments with contractors to replace these with the quality lamps that we have specified.

In the museum area we started to get fittings specifically for museum use in the late 90s. These provided good glare control, lots of useful accessory lenses with different levels of diffusion, beam shaping and high quality UV filtering. At the same time the lamps themselves started to come with UV filtering built in ridding us of one of the few legitimate concerns about usingTH in the museum environment. So for the last decade or so we have had an excellent colour rendering beautifully controllable light source totally in tune with the majority of museum display lighting tasks.

For the last few years we have seen this progressively sacrificed on the alter of “energy saving.” Interestingly the Eurocrats have failed to agree to legislate them out of existence through the Energy Related Projects process. This was supposed to follow on from the Part 1 of domestic lighting however the draft legislation has been endlessly delayed by the awareness that there is nothing in the market that is a realistic alternative. This however has not stopped other limitations on energy use including the Building Regulations in the UK. The lighting manufacturers are also heavily selling LED to the museum market. Many if not most are generally selling similar products to those reliant on LVTH that are frequently twice the price and half the light output. The hype is so strong and so heavily aimed at engineers and building managers with promises of fantastic savings on their energy bills that any aesthetic arguments are blindly overruled.

So what are we left with? In many ways we are returning to challenges we faced in the early days of LVTH. Fittings with poor glare control. LED arrays right at the front of the fitting. As you have a larger lights ource beam control is less good leading to huge fringes of light around your target distribution. Variations of colour between fittings, less bad than it used to be though still a concern with some products. New problems are colour variation over life of fittings. As fittings in many galleries are swapped and changed due to changes in exhibits new fittings will be put beside those that have been running for many hours. They will look different. LEDs MAY have a long life however they do age so fittings of different ages have different outputs. LEDs are a larger area light source or are multiple light sources in one fitting. The majority of our trusted tools for varying distribution do not work the same way. Most LED light fittings are fixed beam angle so instead of swapping a £4 lamp to go from 10° distribution to 45° you need a different and very expensive fitting in many cases. No LED product has a continuous distribution so colour reproduction is just not the same. Most are deficient in the red area of the spectrum leading to problems with reds and skin tones. all have a blue peak. Now we know how damaging UV is and are prepared to exclude it as it generally does nothing for how we see objects. Blue is the most damaging of the visible wavelengths so we need to be aware of this new risk.

The bottom line is that, for now, the quality of museum lighting will go down. In some years time some of these issues will be resolved and the poorer colour rendering will have been accepted. In the meanwhile some objects will have suffered unnecessary damage and some museums will have faced extremely damaging costs of changing over from LVTH to LED, others will have bought expensive LED products that do not live up to promises of quality or life and face costs of replacing systems or fittings bought early on in the development of this technology, around now in fact.

While I always enjoy a challenge and the technological changes that lighting brings I am sad that we seem to be taking a major step backwards in Museum lighting before we can take a step forward on this occasion

Kevan Shaw May 14, 2011