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mondo*arc’s LinkedIn discussion group is open to all and features the latest topics in lighting design and lighting technology. Just search for ‘mondo arc magazine’ in LinkedIn to join.


This month, following lighting designer Kevan Shaw’s article on museum lighting in mondo*arc issue 62, the question is...


Do you agree with Kevan Shaw about the dangers of using LED in museums?


David Bird, Lighting Designer / Director at 2B Designed, Australia • Kevin’s article has much merit and when you consider the embodied energy in LEDs, they may well be even less favourable. Alas I am not aware of the real cost in terms of CO2 emissions in LEDs and therefore it is not possible to know the true payback period. Not addressed at all is the potential use or emissions of other pollutants in their manufacture.


Matt Marshall, Lighting Designer / Project Manager at Klaasen Lighting Design, Singapore • As lighting designers it is up to us to make sure that we are educating others on not only the positives of emerging and new technology but also the the reality in comparison to existing technology as well. LED has many uses and we strive always to use the best lamp choice for the application.


Fred Bass, Managing Director at Neonlite, UK • The lack of LED standards makes it difficult for lighting designers, it forces them to develop their own deep technical understanding of LEDs at chip level when their focus should be on performance & light quality. I agree the technology is moving so fast which makes it difficult to know what’s possible with LED, but right now I believe you can get similar high light quality to halogen sources but with negligible infra-red and virtually no UV, ideal for Museum applications. Also LED solutions that use reflectors can control glare just like the old technology and get precise beam control.


Paul James, Editor at mondo*arc, UK • I had a meeting with a curator and engineers from the National Galleries, London and they were completely sold on LED. Actually thought that LED brought the paintings to life more than LVTH and they calculated savings of “hundreds of thousands of pounds” through carbon tax alone.


Mathijs Sommeijer, Lighting Specialist at Deerns, Netherlands • As a lighting designer I think that the quality of the light is one of the most important aspects when creating a lighting plan for a museum. LED is simply not that good yet compared to halogen light sources. In terms of UV and IR radiation, LED is an interesting option.


Geoff Archenhold, CEO at InGan Research, UK • LED fixtures can deliver the same quality of visible light than Halogen lamps with improvements in efficacy. The main issue is cost as one could obtain a CRI 98 LED system but the cost is more than an 80 CRI based system. One could also use Quantum Dots to modify the LED spectrum and tailor it to meet any spectral output if needs be! I also believe lighting designers should understand as much about technology as possible to understand what it can do. If you cannot understand the fundamentals then why would a client want to employ you? The reason they look for lighting designers and pay them money for their service is for the LD to tell them what is possible with the space and to allow their creative minds to invent new methods of visual expression. I would argue that if you cannot understand what is possible by the technology then you won’t be able to create innovatively.


Paul James • Are we getting too caught up with CRI? It’s only as important as the perception. The guys at National Galleries couldn’t tell the difference between 88 and 95. I suspect they wouldn’t know the difference if the gap was bigger.


Thomas Wensma, Owner at Ambassador Lighting, Netherlands • I agree with Fred and Paul. We should not get too caught up with CRI as it has its limitations. The quality of how well it lights the object has to do with the spectral distribution of the LED being used. We know that most LEDs will favour blue colours much better than Halogen and red colours a bit worse. The better quality LED products will have better phosphor and thus a broader colour spectrum. Manufacturers can optimise their LED products for higher CRI. This is exactly the reason why there does not have to be a difference between a CRI of


Kevan Shaw, Design Director at KSLD, UK • Designers do need to understand the technologies they use in sufficient depth to be aware of all issues each technology brings. We know CRI is a poor measure for colour appearance acceptability. We also know that LEDs that score poorly on CRI can have very high acceptability in test situations, this is particularly noticeable in good warm appearance LEDs.


In respect of who should be arbiters of colour appearance I am not convinced that art experts are always the best to consult. Going back many years I had protracted discussions with curators who thought that 4000K CRI 85 flourescent lamps produced better colour appearance of artwork “... as they are closer to the daylight by which they were painted” irrespective of the fact the light levels were limited to 200lux or 50lux so nothing like daylight! They also forget the fact that many historic paintings were painted with exaggerated colour and contrast specifically to be viewed by candle light. In reality some of the old masters restored with all the old dark varnish removed do look really unhappy in bright cold light. The lack of red in most LED spectra is the biggest problem when looking at art. It does distort deep reds and flesh tones remarkably. Attempts by some LED companies, notably Cree, to add red into the phosphor mix frequently results in an unfortunate pinkish hue to light rather reminiscent of the old “butcher’s” fluorescent lamp to enhance the appearance of meat. I am afraid that a continuous spectrum is necessary to really appreciate colours properly and this is not on offer from LED solutions. Thomas, the idea of tailored spectra is fine in theory but a real non-starter when you try to find an economic solution. No LED manufacturer is going to build stock of all possible options and there will be a significantly large quantity required to manufacture any particular tailored spectrum. Individual museums will not have a realistic economic option to select tailored spectra for different objects in a collection. Basically the flexibility is there but it is all producing solutions that aren’t quite perfect and the technology is not capable of producing the perfect solution!


Thomas Wensma • Tailored spectra is the ‘base’ of LED. Manufacturers are still fine tuning and ‘playing around’ with different spectra. When you improve the phosphor mix there is a continuous spectrum that raises fabrication cost. I don’t suggest to go for many tailored spectra, but LED products are tailored for applications, so the spectra will be tailored accordingly. The solutions aren’t quite perfect but Halogen isn’t either! They are both different and not perfect because of different reasons. Sticking to just colour spectra, they are just different. One is not necessarily better. It’s just that with LED it is really important at the moment to find the products of high quality. The perfect light for a museum is daylight, which will change in its spectral distribution through out the day. Both Halogen and LED will stay the same, both with different spectral characteristics.


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