052 MUSEUM LIGHTING / NATIONAL GALLERY & NATIONAL PORTRAIT GALLERY, LONDON, UK
natural light. SV: Different exhibits need different quanti- ties of light. We were only able to dim down to 80% with the old system (without changing the colour temperature). Now we are able to dim down to 20%. So the beauty of LED lighting is there is no degradation in the quality of light, but it also means we can create more lighting for one exhibit and we can set scenes individually through the ERCO lighting control, which means we can satisfy the curators and conservators whilst using less energy! SV: Throughout the years we’ve used ERCO products so most of the galleries already have the track installed, so with few modi- fications we can adapt the system to LED. This means there is little disruption with high gain and it also means we are future- proofing which is very important. I have been entrusted with our carbon plan and this means we are embarking on projects that are geared up to save carbon in the next ten years. This also includes the car- bon tax that comes into affect in 2012. PJ: Can you explain a little more about the carbon tax and how far it affects you? SV: This is a government tax of (currently) £12 for every tonne of CO2 produced by a business in the UK. This will mean a pay- ment of roughly £100,000 a year from the National Gallery. That’s the equivalent of a couple of exhibitions for us. Therefore it is even more important to see how much money we can save through initiatives like LED adoption as well as our obligation to CRC (Carbon Reduction Commitment Energy Efficiency Scheme). We can save hundreds of thousands of £’s a year purely through energy saving project initiatives, so we look at this partnership with ERCO as an impor- tant part of that. AT: The biggest compliment I could make about the LEDs is that, in the two years since the initiative, we have not had a comment from the public about the lighting system. Nigel Sylvester (NS): That’s a powerful statement! AT: Yes, that means that what we are doing is acceptable because no-one has complained. Believe me we get a lot of complaints about all sorts of things like the
state of the toilets etc, so people would complain if they didn’t like the lighting. PJ: Is there anything that you would say the LED doesn’t quite work so well with? DC: The only thing that I’ve noticed is that LED lighting does not complement three- dimensional objects like works of sculpture so well – at least with the flood lenses on them. I don’t know if it’s the six points of light as opposed to one but it does some- thing to sculpture that evens out some of the plasticity. It wipes out the three-dimen- sional quality of sculpture. Conversely, one of the reasons why we do like its affect on paintings is that it doesn’t over-emphasise frames, which incandescent light can do when the gold jumps out and overwhelms the picture. The LEDs don’t do this yet, they emphasise the surface texture of the painting. NS: This relates to the set of tools you have to do different tasks. In the LED spotlights a special lens determines the beam distribu- tion. The ‘narrow spot’ characteristics are perfect for the play of light and shadow on a sculpture. At the moment you’ve got a great selection of LED characteristics, but there are more options that will become available to you. As it stands, from the same fitting, you can have five different beam distributions just by changing the lens. AT: In our gallery people say that they can pick out different elements like quartz in the marble now, when using LED. NS: Yes, what I saw was something that was better than when the halogen was used because it picked out all the content of the sculpture material. The detail came alive. PJ: Is that because of the different colour temperature, though? SS: It’s more about the different mix of colours in the beam. Tungsten has got a massive emphasis on red, whereas LED has a more even distribution between the blues and the reds. There is a spike in the blue that we’re trying to flatten out, but you haven’t got lots of red beam thrown onto every object that makes it look dirty and yellow. DC: One of the problems that you’re facing with the acceptance of LED lighting is that we have made people accustomed to seeing
works of art blasted with warm spotlights. It’s simply what they are used to. SV: People don’t like change. AT: The biggest criticism I’ve heard is regarding the colour rendering – the fact that it’s not in the 90s and losing the warm effect. NS: There are two points to consider with the Colour Rendering Index. The first is that a CRI number cannot guarantee what you are going to see and the second is there is a compromise to be had in terms of luminous efficacy. We want you to have a performing product with a very good illuminance on the articles you are illuminating with a good colour rendering. If you try to increase the colour rendering any more, you inevitably reduce the light output. SV: Yes, of course colour rendering is im- portant but it’s only as good as your eyes. It’s all about human perception. Can you distinguish between an LED fitting with a CRI of 88 and something with a CRI of 95? My guess is no. DC: Yes, for the vast majority of people you’re not going to see the difference. Just seeing the quality of light in Room 13 made up our minds about that.
PJ: The other issue is people’s perception of what colour rendering is. They may be actually thinking about colour appearance, different colour temperature for instance. SV: Exactly. LEDs are not comparative to tungsten so therefore it’s questionable whether you should use CRI as a measuring device of quality. NS: I think LED lighting is a major chapter change and it’s galleries like yours that are at the forefront of this change. We are so used to warm light but the cooler light of the LED is a better representation of day- light and that is the optimum environment for viewing paintings. SV: In fact, when you move from a tung- sten-lit gallery to an LED-lit one the percep- tion is that the LED gallery is brighter. This isn’t the case – it’s the perception. This means you can dim the LED lighting even further to get the same perceived illumi- nances thus saving more energy. AT: I’m also using less air conditioning, based upon our figures, because there
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