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Newsletter Volume 10. Issue 5. Sept/Oct 2017

The Society of Light and Lighting

Part of the Chartered Institution of Building Services Engineers

LIGHTING IN FLUX The Trotter Paterson lecture

PAST AND FUTURE Waxing lyrical on candle and laser



Secretary Brendan Keely FSLL SLL Coordinator Juliet Rennie Tel: 020 8675 5211 Editor Jill Entwistle Communications committee: Gethyn Williams (chairman) Rob Anderson Iain Carlile MSLL Jill Entwistle Chris Fordham MSLL Eliot Horsman MSLL Mark Ingram MSLL Stewart Langdown MSLL Linda Salamoun MSLL Bruce Weil All contributions are the responsibility of the author, and do not necessarily reflect the views of the society. All contributions are personal, except where attributed to an organisation represented by the author.

Copy date for NL 5 2017 is 22 September Published by The Society of Light and Lighting 222 Balham High Road London SW12 9BS ISSN 1461-524X © 2017 The Society of Light and Lighting The Society of Light and Lighting is part of the Chartered Institution of Building Services Engineers, 222 Balham High Road, London SW12 9BS. Charity registration no 278104

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Years ago at a pecha kucha session at BDP, people involved in lighting were invited to talk about influences, and aspects of illumination they enjoyed. Anyone who came up with a cliche was pelted with ping pong balls (who knew lighting could be such fun?). More than one of us braved the bombardment and mentioned candlelight on the grounds that hackneyed though it may be, we all knew it was our favourite light source. The sentiment was confirmed at a recent SLL event at London’s Sam Wanamaker Playhouse, the Jacobean equivalent of Shakespeare’s Globe (see Past and Future, p9). Apart from some occasionally used LED-simulated daylight, the theatre is authentically lit entirely by candlelight. The result is, of course, magical and multi-sensory, the

candles lending not only the perfect colour temperature to the space and the performance but also their dynamism, their smell and the faint crackling sound of their burning. But as theatre expert and academic Martin White spoke of the history and research into their use, what became apparent was how many considerations chimed with those for a contemporary setting. The dimming facility may have relied on raising and lowering the chandeliers (surprisingly effective), but the 17th-century sensibility of the importance of colour, material and finish, and how they should be an integral part of the lighting experience, was every bit as modern as that of today’s designer. Candlelight ‘was not an isolated component of the indoor theatrical experience,’ says White. ‘There is an ecology of lighting of which the candles themselves are just one part.’ The colours and textures of the painted surfaces were crucial, he says,with a high degree of gilding applied to catch the light. Costumes and even make-up (with crushed pearls or oyster shell) were designed for luminescence and lustre. The future aspect of the presentation, a glimpse of the potential of the next big thing, laser diodes, was also fascinating. But it felt important not to disregard the lessons of the past. Jill Entwistle

Current SLL lighting guides SLL Lighting Guide 1: The Industrial Environment (2012) SLL Lighting Guide 2: Hospitals and Health Care Buildings (2008) SLL Lighting Guide 4: Sports (2006) SLL Lighting Guide 5: Lighting for Education (2011) SLL Lighting Guide 6: The Exterior Environment (2016) SLL Lighting Guide 7: Office Lighting (2015) SLL Lighting Guide 8: Lighting for Museums and Galleries (2015) SLL Lighting Guide 9: Lighting for Communal Residential Buildings (2013) SLL Lighting Guide 10: Daylighting – a guide for designers (2014) SLL Lighting Guide 11: Surface Reflectance and Colour (2001) SLL Lighting Guide 12: Emergency Lighting Design Guide (2015) SLL Lighting Guide 13: Places of Worship (2014) SLL Lighting Guide 14: Control of Electric Lighting (2016) LATEST SLL Lighting Guide 0: Introduction to Light and Lighting (2017) SLL Lighting Guide 16: Lighting for Stairs (2017) Guide to Limiting Obtrusive Light (2012) Guide to the Lighting of Licensed Premises (2011)

Secretary’s column

‘Featuring experts from around the globe, this will be fascinating for anyone interested in lighting museums’ We will be in Dubai at Light Middle East from 17-19 October, where we will also be delivering the second Ready Steady Light Middle East. We hope many of the UAE members will come along and meet with myself and SLL president Richard Caple at the exhibition to discuss news and publication updates, as well as opportunities to upgrade membership and take part in Ready Steady Light. From 1-4 November we will be at the Professional Lighting Design Conference (PLD-C) in Paris and especially keen to see The Challenge competition. Good luck to Team Jeff Shaw. LuxLive and the Lux Awards take place on 15-16 November. We will be exhibiting again so you have the opportunity to be updated with events, publications and upgrades to membership. The finals of Young Lighter of the Year will take place there, as well as other events. The line-up for the lighting session at the CIBSE Build2Perform at London’s Olympia is excellent and includes: designing for wellbeing through daylight, control systems and the issues surrounding retaining your specification. The lighting session will take place on the first morning of the two-day event, on 21 November, and we hope to see you there.

Editorial2 Secretary’s column


News4 Lighting in flux Based on his recent Trotter Paterson Lecture, Peter Boyce outlines the key issues which lighting must address in future


Past and future 9 An SLL event at the Sam Wanamaker Playhouse looked backwards and forwards in time. Stephen Thompson talks to speakers Martin White and Paul Rudy about lighting that ranged from the simple to the highly sophisticated: Past: worth the candle Martin White on the impact of candlelight in theatre Future: laser vision Paul Rudy outlines what may be the next major light source



Preference and perception 15 Iain Carlile singles out four recent LR&T papers on colour temperature and lighting method Cover: Corrs Chambers Westgart office, Perth, Australia, Award of Merit winner in the 2017 IALD Awards. Lighting by Electrolight

Photography: © Pieter Naessens © Peter Clarke

We need to talk about LR&T… The world-renowned, peer-reviewed Lighting Research and Technology journal will be celebrating its 50th anniversary in 2018. We will obviously be acknowledging the anniversary throughout 2018 but one of the journal’s contributors, Christopher (Kit) Cuttle will be presenting a warm-up lecture for the society on the evening of 10 October 2017 at UCL. We invite all to attend this event to get an insight into the latest research in lighting application. Bookings for this lecture (free to attend) can be made through the SLL website. A big thank you goes to Peter Boyce, technical editor of the LR&T journal, who delivered the 2017 Trotter Paterson lecture at Bishopsgate Institute in July (see p5). We will be sending out links to the lecture to view online once the editing is complete. The closing date for entries to the lighting category of the Building Performance Awards is looming with the deadline of 15 September. Can you prove to the judges that not only can you create quality lit environments but you can also achieve this with minimum energy consumption? All details are on the CIBSE website ( The call for abstracts has been made for the CIBSE Technical Symposium which will take place from 12-13 April 2018 at London South Bank University. The 250-word abstracts are due in by 11 September so there’s still time to get involved in the lighting sessions. The Night of Heritage Light and Pockets of Light 2018 will be held in Oxford on the evening of 29 September alongside the Curiosity Carnival (see p4). The society’s members will be lighting seven of the city’s finest building facades including the Ashmolean Museum, Museum of Natural History and Pitt Rivers Museum, and the Radcliffe Camera. If you are in the area you will enjoy the spectacle and if you

can lend a hand on the evening, please do get in touch – all assistance will be appreciated. Please do spread the word to others. This year we have three schools from Oxford taking part in Pockets of Light. The engagement and workshops are complete, the designs are in and the judges will be reviewing the entries from the students with the winning designs lighting the facades of the courtyard of the Bodleian Library. Meanwhile it’s conference and exhibition season. From 11-12 September we have the inaugural Museum Lighting Symposium and Workshops with the Centre for Doctoral Training in Science and Engineering in Arts Heritage and Archaeology (SEAHA) at UCL. Featuring experts from around the globe, this will be fascinating for anyone interested in lighting galleries and museums.



For up-to-date information follow us on Twitter @sll100




Third Night of Heritage Light event moves to Oxford The third Night of Heritage Light event will be held at the end of this month. This time it will take place in Oxford, alongside the Curiosity Carnival, on 29 September. SLL members will be lighting the facades of seven of the city’s key historic and research buildings, including the Ashmolean Museum, Museum of Natural History and Pitt Rivers Museum, and the Radcliffe Camera (pictured left). The society is again emphasising the educational aspect by running the second Stem-focused Pockets of Light exercise with local schools. There have been three PoL workshops at City of Oxford College, Saint Gregory the Great secondary school, and North Kidlington primary school respectively. The workshops have resulted in the schoolchildren submitting lighting designs for the facades of the courtyard of the Bodleian Library. ‘We have had the opportunity to talk about light and lighting to more than 70 students in total and now have around

New ILP president calls for more lighting promotion The Institution of Lighting Professionals must do more to promote the value and importance of lighting and lighting technology to the wider public, new president Alan Jaques said in his inaugural address. Smart and connected lighting were transforming the industry, he said, and it was essential to be at the heart of the debate on how these new technologies could best shape both public and private environments. Jaques is practice manager for lighting systems at Atkins and takes over as

president from Kevin Grigg, regional sales manager for Urbis Schréder. Jaques stressed the importance of the lighting profession as a whole doing more to communicate the value and importance of lighting design and engineering. ‘What we do makes a difference, in a way that impacts on everyone’s lives on a daily basis. We need to be better at getting this message out to a wider audience.’ l Dave Ribbons, Lutron’s director of sales Europe and Africa, has taken over from Peter Scott of Fern-Howard as president of the LIA Council of Management.

Wellbeing tops agenda at Build2Perform session The wellbeing of building occupants will be the key theme of the lighting session organised by the SLL as part of CIBSE’s new Build2Perform event in November. The half-day session will set out the range of considerations to be taken into account when designing, procuring and delivering natural and circadian lighting in buildings. In addition to considering circadian rhythms in a scheme, speakers will also examine issues such as the ethics of replicating daylight patterns to manipulate human response. Speakers will include Andrew Bissell



of Cundall Light4, Arfon Davies of Arup, John Mardaljevic, professor of Building Daylight Modelling at the University of Loughborough, Iain Ruxton of Speirs and Major, and DHA’s Peter Fordham. Chairing the session will be president elect Iain Carlile, associate of DPA Lighting Consultants. Build2Perform will take place on 21-22 November at Olympia, London. The lighting session will run from 10am-12.30 on Tuesday 21 November. More details at

70 excellent designs,’ said Richard Caple, SLL president and co-organiser with Simon Fisher. ‘We will be picking a winner from each school and hopefully turning their designs into reality on the night.’ NoHL aims to promote lighting as both an art and a science. For one night only, lighting professionals will showcase the practical applications of lighting, and demonstrate how it can improve and enhance architecture and the night-time environment. The Curiosity Carnival is part of a Europe-wide celebration of European Researchers’ Night. A city-wide programme of activities offers an opportunity to meet researchers and discover how research affects and changes people’s lives. Night of Heritage Light and Pockets of Light takes place on Friday 29 September. Anyone interested in helping on the night should contact Juliet Rennie (

On the lighter side... On the whole despoiling nature with lurid lightshows more fit for a funfair than a forest is perhaps not to be endorsed. But then along comes an exquisitely seductive installation. Or series of installations in this case, in the 500,000sqm Mifuneyama Rakuen Park in Japan’s Saga Prefecture. Sponsored by cosmetics company Shiseido and created by teamLab, the 14 deeply immersive digital installations create a journey through the forest surrounding an ancient mountain. A poetic response to the landscape, they enhance both natural and manmade features to breathtaking effect. ‘The concept of the project is that non-material digital art can turn nature into art without harming it,’ says teamLab. The exhibition runs until 9 October. Experience it at www.teamlab. art/e/mifuneyama2017/

Trotter Events: Paterson Masterclass Lecture 2013/14 2017

Lighting in flux For more than 50 years lighting practice has been driven by two objectives, two measurement systems, five metrics and one assumed location. The two objectives are good visual performance without visual discomfort. The two measurement systems are photometry and colorimetry. The five metrics, which you will find in most lighting recommendations, are maintained illuminance, illuminance uniformity, correlated colour temperature (CCT), colour rendering index (CRI) and unified glare rating (UGR). The assumed location is the horizontal working plane. Today, almost all these aspects of lighting are being questioned. The answers to these questions have the potential to put lighting practice into a state of flux. I wish to start with the most fundamental of these questions: what to do about photometry? The problem with photometry is that all the photometric quantities used to quantify light sources, luminaires and lighting installations – luminous flux, luminous intensity, illuminance and luminance – rely on the CIE photopic luminous efficiency function (V(λ) to convert radiometric quantities to photometric quantities. Unfortunately, V(λ) is based on the response of only two of the five photoreceptor types in the human retina: the long wavelength sensitive and medium wavelength sensitive cones that dominate the fovea. This means that the photometric quantities are biased towards the detection of detail.

Making detail visible is always likely to be important but today it is not the only objective of lighting and these other objectives, such as the perception of brightness and colour, off-axis performance and circadian stimulation, involve some of the other photoreceptors such as the short-wavelength sensitive cones, the rods and the intrinsically photosensitive retinal ganglian cells. The five photoreceptors operate in different combinations under different conditions and are connected in different ways to achieve different objectives. This means that the human visual system has multiple spectral sensitivities and some of these spectral sensitivities differ markedly from V(λ)1.

‘If even some of these changes occur the result will be a greater complexity in design because of the diversity in objectives and a greater number of metrics’ A number of ways have been proposed to correct this situation. One is to do nothing and accept that the visibility of detail is all that matters for lighting. The most radical is to abandon photometry altogether and use radiometry within fixed wavelength limits, say 380nm to 780nm. Alternatively, the system of universal photometry proposed by Rea2 could be adopted. This would mean having a spectral sensitivity envelope that covers the response of all retinal photoreceptors @sll100


Based on his recent Trotter Paterson Lecture, Peter Boyce outlines the key issues which lighting must address for the future


Trotter Paterson Lecture 2017


for use by manufacturers and regulators3 while applying the different spectral sensitivities to different design objectives. Such proposals are likely to be strenuously opposed by important institutions but the concept of different spectral sensitivities for different design objectives is important and therefore is likely to find its way into practice, if not by dictat then because it is useful. Turning now to colorimetry, the question here is how to quantify the multi-faceted aspects of colour perception. CRI is essentially a measure of colour fidelity, in other words how accurately a test light source renders a set of colours relative to a reference light source. Colour fidelity can be important

but it is not always enough. Other aspects of colour such as naturalness and vividness can affect light source preference. This is why there have been numerous suggestions for at least one additional metric related to the degree of colour saturation4,5. IESNA has published a new approach to colour metrics6 involving an improved fidelity metric, a gamut area metric and, most interestingly, a graphics approach rather than a single number, similar to that advocated by van Kemenade and van der Burgt7. There is little doubt that new colour metrics will soon be advanced although how many will depend on the balance struck between the complexity of colour perception and the simplicity required for widespread adoption. Other design metrics under question are illuminance uniformity and UGR. Illuminance uniformity is the great unexplored variable in lighting design. This is because the logistics needed to carry out investigations are inhibiting but a recent study by Narendran et al has shown the potential benefits

in terms of the perception of safety and energy savings of enhanced uniformity in parking lots8. As for UGR, this has been shown to be incapable of accurately predicting discomfort glare for very non-uniform luminaires9. Consequently, a number of improved UGR models have been developed10,11 but I doubt if any of them have a future because the simplest solution to this problem is for luminaire manufacturers to hide any direct view of LEDs. When this is done UGR is an effective predictor. Another area of concern is the use of the horizontal working plane as a location for design. For many years attempts have been made to direct designers’ attention to the task plane, wherever that may be, and to the value of a task ambient approach12, but to little effect. Now Cuttle has come along with a more radical approach. He argues that current lighting standards are more than enough for good visual performance on virtually all tasks so rather than lighting the task, attention should be given to lighting the space13. This means the basic lighting criterion should be the perceived adequacy of illumination and for this the right metric is the mean room surface exitance. Adopting this metric would emphasise the illumination of the major room surfaces such as the walls and ceiling, and make indirect lighting more efficient than direct lighting. The risk in doing this is that the room becomes a white box. To avoid this outcome, Cuttle suggests a second metric called the task/ ambient illumination ratio which enables a hierarchy of lighting to be established14 for the sake of creating some interest15. For this approach to be adopted will require a demonstration of its value and some software developed to make it easy to use16. By now it should be clear that lighting is not short of ideas for improvement so it is interesting to ask why. I believe there are three reasons. First, there has been a steady development in understanding the subtleties of the impact of exposure to light on both the visual and non-visual systems. Second, we are in the middle of a major transition to solid state lighting and sophisticated controls, offering much greater flexibility in the amount, spectrum and even light distribution of light sources and luminaires. Third, there is a need to introduce objectives beyond good visual performance without visual discomfort if lighting is to avoid becoming a simple commodity. The first and last of these reasons deserve some discussion. The discovery of the intrinsically photosensitive retinal

Spectral sensitivity for foveal visual acuity

Spectral sensitivity for the perception of large field brightness

‘There is a need to introduce objectives beyond good visual performance without visual discomfort if lighting is to avoid becoming a simple commodity’



Trotter Paterson Lecture 2017

‘The concept of different spectral sensitivities for different design objectives is important so is likely to find its way into practice, if not by dictat then because it is useful’

ganglion cells in the human retina17 has revealed a new field of lighting effects. The physiology behind these effects is partly understood but there is still a great deal to learn. What is clear is that the response of the visual system to light is sensitive, fast, detailed and located, while that of the non-visual system, or more correctly the non-image-forming system, is relatively insensitive, slow, crude and non-located. This division in characteristics does not mean that the two systems are completely separated. They are not. The rod and cone photoreceptors that dominate the visual system also have a role to play in the non-visual system and the intrinsically photosensitive retinal ganglion cells influence some non-imaging forming aspects of vision such as pupil size. Of all the possible non-visual effects of light exposure the one that has been most extensively studied is that of melatonin concentration, this being a hormone circulating in the bloodstream that is used to synchronise the timing of many different functions of the body. Exposure to a regular day/night light pattern is necessary to entrain the circadian rhythm shown by melatonin but exactly what form that pattern should take is still under discussion. For example, there is no international agreement over the spectral sensitivity of the circadian cycle based on melatonin suppression or what constitutes the necessary amount of light or dark. Further, the consequences of light exposure are known to depend on the timing and duration of light exposure over the whole 24 hours as well as the prior photic history of the individual being exposed. Given this situation it is hardly surprising that there are few lighting applications devoted to improving the operation of the circadian system. Those that have been shown to be beneficial are typically concerned with people who have damaged circadian systems, for example, those with dementia18, or who have disrupted circadian systems, such as people working rapidly rotating shift systems19, or who have very limited opportunity for a light/dark exposure pattern, as in the case of submarine crews20. It remains to be determined if people who regularly


Basic structure of the IESNA TM30 method for colour rendition

work by day and sleep at night benefit from lighting designed to stimulate the circadian system. As for the need to develop new objectives for lighting, this is where we enter the realm of human-centric lighting. Humancentric lighting is lighting designed to bring out the full range of effects that exposure to light can have ranging from the familiar visibility and visual comfort to increased alertness, better mood and motivation, and improved health and wellbeing. To some, human-centric lighting is nothing more than a commercial bandwagon designed to sell product while for others it is a legitimate approach to better lighting quality. Human-centric lighting can be considered to have both a width and a distance. The increased width is evident from the list of potential effects given above. The distance occurs because whereas visibility and visual comfort can be closely related to lighting conditions, the other effects are related to many factors, lighting conditions being just one of them. This is particularly so when the outcomes claimed, such as better learning in schools, are far removed from the more obvious effects of lighting. Given this situation, what is the designer to do? One answer would be to ask a series of questions of anyone claiming some remote effect for lighting: is the claimed effect statistically significant? If it is, then what is the size of the effect and is it worth bothering about; has the effect been replicated; what is the mechanism for the effect and are there any converging measures that support the role of lighting? The answers to such questions can sort the wheat from the chaff. There are undoubtedly benefits of lighting beyond good

Conventional CIE luminous efficiency function (V lambda) and the proposed universal luminous efficiency function @sll100


Trotter Paterson Lecture 2017

‘Such a situation will undoubtedly call for greater transparency from both designers and manufacturers if confusion and chicanery are to be avoided’


visual performance without visual discomfort but until the claims made for human-centric lighting are examined with rigour, then doubts about their validity will continue to be expressed. To sum up, general lighting practice is likely to be entering a period of flux over and above that already occurring with the rapidly spreading use of solid state light sources. Any changes to photometry and colorimetry metrics other than a simple replacement of CRI will require a lot of work by those who manufacture lighting equipment, those who prepare lighting recommendations and those who design lighting installations. Similarly, changing the primary purpose of lighting from lighting the task to lighting the space will require a very different approach by designers. Where the non-visual effects of light exposure can be shown to be beneficial, different types of lighting may be required, as they will where the claimed human-centric effects of light can be shown to be reliable and sizeable. If all or even some of these changes occur the result will be a greater complexity in design because of the diversity in objectives for lighting and a greater number of metrics to describe lighting. Further, for many of these objectives the outcome will become a matter of probability rather than certainty. Such a situation will undoubtedly call for greater transparency from both designers and manufacturers if confusion and chicanery are to be avoided. Finally, it is a pleasure to acknowledge the contributions of Mark Rea and Kit Cuttle to many of the thoughts expressed. Although separated by thousands of miles, modern communications have enabled many stimulating discussions with them for which I am extremely grateful. It is only fair to say that while they would undoubtedly agree with some of the content of this article and the lecture you can be sure that they would not agree with all of it.

The Trotter Paterson lecture, organised by the SLL, was delivered by Peter Boyce, FSLL, on 6 July at London’s Bishopsgate Institute



References 1 Rea MS. Value Metrics for Better Lighting, Bellingham WA; SPIE Press, 2013 2 Rea MS. The lumen seen in a new light: Making distinctions between light, lighting and neuroscience. LR&T 2016; 48: 259-280 3 Rea MS, Bierman A. A new rationale for setting light source luminous efficacy requirements. LR&T. First published 10 September 2016 DOI 1477153516668230 4 Lin Y, Wei M, Smet KAG, Tsukitani A, Bodrogi P, Khanh TQ. Colour preference varies with lighting application. LR&T 2017; 49: 316-328. 5 Teunissen C, van der Heijden FHFW, Poort SHM, de Beer E. Characterising user preference for white LED light sources with CIE colour rendering index combined with a relative gamut area index. LR&T 2017; 49: 461-480. 6 Illuminating Engineering Society of North America. Technical Memorandum TM-30-15 IES Method for Evaluating Light Source Color Rendition New York: IESNA, 2015. 7 van Kemenade, JTC, van der Burgt PJM. Light sources and colour rendering: Additional information for the Ra Index, Proceedings of the CIBSE National Lighting Conference, Cambridge, London: CIBSE, 1988. 8 Narendran N, Freyssinier JP, Zhu Y. Energy and user benefits of improved illuminance uniformity in parking lot illumination. LR&T 2016; 48: 789-809 9 Tashiro T, Kawanabe S, Kimura-Minoda T, Kohko S, Ishikawa T, Ayama M. Discomfort glare for white LED light sources with different spatial arrangements. LR&T 2015; 47: 316-337 10 Scheir GH, Donners M, Geerdinck LM, Vissenberg MCJM, Hanselaer P, Ryckaert WR. A psychophysical model for visual discomfort based on receptive fields. LR&T. First published 29 July 2016 DOI 1477153516660606 11 Yang Y, Luo MR, Ma SN. Assessing glare Part 2: Modifying unified glare rating for uniform and non-uniform LED luminaires. LR&T. First published 5 April 2016 DOI 1477153516642622 12 British Standards Institution, (2011a) BS EN 12464-1:2011 Lighting of Workplaces – Part 1 Indoor Workplaces, London: BSI. 13 Cuttle C. Towards the third stage of the lighting profession, LR&T 2010; 42: 73-90. 14 Cuttle C. A new direction for general lighting practice, LR&T. 2013; 45: 22-39. 15 Hawkes RJ, Loe DL, Rowlands E. A note towards the understanding of lighting quality, Journal of the Illuminating Engineering Society 1979; 8: 111-120. 16 Cuttle C. Lighting Design: A Perception Based Approach. Abingdon, UK: Routledge, 2015 17 Berson DM, Dunn FA, Takao M. Phototransduction by retinal ganglion cells that set the circadian clock, Science 2002; 295: 1070-1073. 18 Riemersma-van der Lek RF, Swaab DF, Twisk J, Hol EM, Hoogendijk WJ, van Someren EJ. Effect of bright light and melatonin on cognitive and non-cognitive function in elderly residents in group care facilities: a randomised controlled trial, JAMA 2008; 299: 2642-2655. 19 Eastman CI. Circadian rhythms and bright light recommendations for shift work, Work Stress 1990; 4: 245-260. 20 Young CR, Jones GE, Figueiro MG, Soutiere SE, Keller MW, Richardson AM, Lehmann BJ, Rea MS. At-sea trial of 24-hour-based submarine watchkeeping schedule with high or low correlated colour temperature light sources. Journal of Biological Rhythms 2015; 30: 144-154

SLL event: Past and Future

Past and future A recent SLL event held at the Globe’s Sam Wanamaker Playhouse in London simultaneously looked backwards and forwards in time, moving from candlelight in theatre to pioneering laser diode technology. Stephen Thompson talked to speakers Martin White and Paul Rudy about lighting that ranges from the simple to the highly sophisticated

For many years prior to the opening of indoor playhouses, there had been indoor performances involving a temporary touring set-up playing in the homes of the nobility. When the first outdoor playhouse opened in 1565, it would have been a huge step for acting companies to get used to this completely new performance space. The next fundamental change was when indoor performance returned, but taking place in a fully equipped professional playhouse. Most importantly there was the need now for intervals in plays. Candlelight is a simple technology, but what they have learned at the Sam Wanamaker Playhouse is how flexible it is. A skilful stage crew, often involving the performers themselves, can change the candlelight with surprising ease and speed, so that the performing space changes as the text requires, perhaps for moving the scene’s location, for the implication of passing time, or for transforming the atmosphere. This therefore gives the play its own particular structure and rhythm. Rather than using the modern term ‘interval’, it is perhaps more useful to think of them as pauses; moments when the audience could perhaps stretch their legs and briefly chat to each other. Outdoor performances on the other hand were played straight through, which would have a very different feel. For instance, in Shakespeare’s The Winter’s Tale, which would have been performed outside, Time is an allegorical figure literally played by an actor explaining to the audience that 16


Martin White is emeritus professor of theatre at the University of Bristol, and senior research fellow and theatre associate at Shakespeare’s Globe. Alongside Paul Russell, the SWP’s production manager, he talked about lighting the Playhouse and the impact of candlelight within indoor playhouses

years have passed in the narrative of the play. In an indoor playhouse, however, candles would have been extinguished or lighted, involving adjusting the height of the candelabras, out of technical necessity, and so creating a pause which is itself a literal passing of time. Martin White’s main argument is that the intervals were not inserted just so that the lighting could be changed, but intervals would nevertheless have been necessary because the lighting needed to be changed. ‘The lighting is god,’ as he puts it. ‘The lighting indoors must be that which will control everything else you do.’ No one knows how many of these pauses there were. However, clues can be found in the study of texts by those playwrights who clearly wrote for indoor playhouses. For instance, in Ben Jonson’s The Magnetic Lady there are two ‘spectators’ of the play (actually played by company actors) who comment between the acts throughout the play on its shortcomings, eventually encouraging the actors not to stay for the last act. Jonson is acknowledging and playing with the notion here of the audience’s impact on an indoor performance in a way that would not have been possible in an outdoor performance, where the standing audience are free to come and go as they please without interference. So the indoor playhouses would have had a very different rhythm; different even from the one they have in the present day in

Pete Le May

Past: worth the candle

Candles bring a unique and sensuous dimension to performance



SLL event: Past and Future

Background In 2014, Shakespeare’s Globe in Southwark, London, opened the Sam Wanamaker Playhouse, a recreation of an indoor 17th-century Jacobean playhouse to stand alongside its reconstruction of the outdoor Elizabethan Globe Theatre that opened in 1997. Authentically, and to great dramatic effect, it is lit with candles – in the form of specially designed chandeliers above the stage, pillar-mounted sconces and with portable devices carried by the actors. The original indoor playhouses (often termed ‘private’ to distinguish them from openair ‘public’ playhouses such as the Globe) were lit by candles, and had the capacity to shutter their windows to vary the amount of daylight they admitted. Until the introduction of gas lighting in the 1820s, illumination in British theatres would continue to be provided by candles or oil lamps (often both in the same playhouse).

‘It becomes everyone’s job to work out how they can do it – even if that means that in your production of Othello you would like a candlelit mirror ball’ to describe it. Martin says that room is a word the playwrights often use for the space: in Philip Massinger’s play The Roman Actor, performed at the Blackfriars indoor playhouse, the words



Mark Douet


the Wanamaker Playhouse. White believes it is a rhythm that we have inevitably now forgotten. Some plays were performed both indoors and out, but the experience of watching them would have been very different in each setting. In White’s view, John Webster’s The Duchess of Malfi was clearly written for indoors, although it is known that it was performed outdoors too. He feels that something of the impact of Webster’s play would be lost in outdoor performance because only indoors could the light levels be controlled to match the emotional path of the play. White cites John Ford who wrote the majority of his plays for the same company which did not have an outdoor venue. His plays are about people who are at the edge of an experience before a fall into disaster. His disturbing plays display violence, sexual tension and intense emotions. It is a generalisation to say that his characters and plots are shaped by the indoor performing space he is writing for – Shakespeare too writes characters with acute psychological detail in extreme situations – but because the setting of the play can now easily become so small, because there can now be written a scene with two characters whom only the audience can see, it is tempting to compare the intense intimacy of the indoor playhouse space with Ford’s exploration inside his characters’ minds. Indeed so close are players and spectators in the tiny Sam Wanamaker Playhouse, the word room often comes to mind

Rome and room are merged so that they become the same place. The lighting of an indoor playhouse ‘room’ would be as recognisable to the audience as the lighting in the rooms of houses, bearing in mind that for most people seeing the much greater number of candles burning in the playhouse might have been akin to the pleasure and surprise of today’s Christmas decorations and light festivals. And live candles would bring from house to theatre their uniqueness as a lighting source, because they also smell and quietly crackle. The present day Sam Wanamaker Playhouse is a unique construction based on the interpretation of a whole series of documents from different places, rather than being the reconstruction of a specific theatre. The result of these interpretations is that the plays, the space and the lighting do all work together. White usually meets the directors and designers before they start formulating their production plans, and tells them not to concern themselves with how things can be done, but to focus simply on what they want to do and what effects they want to create. After that it becomes everyone’s job to work out how they can do it – even if that means that in your production of Othello you would like a candlelit mirror ball. White has been pleasantly surprised to see both how much variation directors and designers have found, but also to see that some stop adjusting the lighting so much as the production process evolves. He believes the production has to come first in order to prevent the Wanamaker from becoming a ‘museum exercise’, but for whatever is created on stage, however the lighting is used, the present continues to be formed by the past. As he says, ‘everything must work to the candlelight’.

The Duchess of Malfi, the first production at the Playhouse. The permanent rig is supplemented by a series of handheld devices

Allies and Morrison

SLL event: Past and Future

Martin White outlines the research and thinking that lay behind the lighting of the Sam Wanamaker Playhouse The first question to answer was clear: real or artificial candles? There were some cautious views that we would be unlikely to be licensed to perform publicly in a wooden theatre using live flame. But from the start I was convinced that this was the fundamental issue that had to be resolved. I’m often told how ‘realistic’ artificial candles can appear, especially as technologies have advanced, but I remain unconvinced. The reason is simple: the candles – like the actors and audience – are live, and their light plays with the textures of costumes and paint finishes in a way quite distinct from artificial versions. Fortunately, the London Fire Brigade felt the same way. A crucial meeting, attended by key parties, was held to put the case for allowing live flame. The first topic was, of course, safety, both for the audience and the actors: the nature of the candles we intended to burn, the fixings we would use in the chandeliers, the particular stewarding arrangements and evacuation plans proposed, all contained in the crucial candle management strategy and risk assessment documents. But what was especially heartening was the LFB's obvious interest in why it was so important that the candles should be live, beyond the desire for historical accuracy, and their clear

understanding of the aesthetic significance of candlelight. Their decision to allow us to perform in candlelight remains, for me, the watershed moment in the whole project. With the LFB support secured, we could now turn our attention to specific and fundamental practical issues. I had assured the LFB that no candles would be suspended above the audience and that we proposed to burn only wax candles with modern braided wicks instead of the rolled wicks used in the 17th century. The early modern theatres burned both candles made from beeswax and those made from tallow (essentially animal fat from sheep or beef). Much that is written about tallow overstates the degree to which it smells and smokes, but there is no doubt that the candles can burn less predictably than wax, they break easily when handled and are hard to store, which is a crucial factor for a theatre. The standard size of an early modern theatre candle (wax or tallow) was 10.5 inches long (27cm) and 0.75 inches (2cm) at the base, tapering (because made by dipping) towards the wick, and there is no significant difference in light output between wax and tallow. (Experiments undertaken at the Baroque Theatre Institute in Cesky Krumlov in the Czech Republic confirmed my own findings, and in this, and many other areas of research and practice, the project owes a great debt of thanks to the institute and its director, Dr Pavel Slavko.) @sll100



CGI of the Sam Wanamaker Playhouse interior. The six chandeliers, each with 12 candles and mounted 2.4m above the stage, are supplemented by sconces mounted on the pillars. Dimming is a simple matter of raising and lowering the chandeliers

SLL event: Past and Future

Pete Le May

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This is an edited extract of an article by Martin White that first appeared in Lighting Journal in April 2014

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are of most glory’. The silver thread in costumes was similarly designed to catch the light, as indeed was the actors’ makeup, gleaming with a lustre derived from crushed pearl or oyster shells, and their collars and ruffs reflecting the light to their faces. The total effect must have been captivating. Candle technology is basically simple. But what I have discovered is just how flexible it is, varying the ambient light using the shutters, creating different light levels by adjusting the height of the chandeliers or extinguishing lights in the sconces, and using gentle additions with lanterns or strikingly dramatic effects with torchlight. The early production of John Webster’s 1614 masterpiece, The Duchess of Malfi, demonstrated the impact of the candlelight, with reviewers praising how it revealed the play quite differently from a conventionally lit production.

I knew that the candles would be positioned in chandeliers above the stage and in sconces on the pillars supporting the upper gallery (all the lighting instruments were made for the SWP by Penny Spedding, an artisan metal worker), but I needed to ascertain how many candles we would burn. The Globe is committed to the idea that any decision regarding the historical aspects of its theatres should have some root in the early modern period, but where the use of candles is concerned the evidence is thin on the ground. Only one reference is known that refers directly to a commercial indoor playhouse (the Salisbury Court, built in 1629) and that is itself rather vague, leaving it unclear the ratio of wax to tallow that was purchased. However, my analysis of this reference led me to a possible range from 102 (if all tallow) to 25 (if all wax), and a conclusion of an average of 66 (54 tallow, 12 wax). I then looked at records of performances at court by professional actors (where, unlike a commercial theatre, cost was presumably not a constraint) and found that an indicative range was between 60 and 90 candles being used in spaces comparable to that of the Sam Wanamaker Playhouse. As a result, at the SWP, we have so far burnt 72 in the six chandeliers with a further 24 five-inch (13cm) candles in the sconces. Rather than the lofty position often seen in illustrations of old theatres, the chandeliers are hung exactly eight feet (2.4m) above the stage, a height supported by the little evidence there is. This ‘permanent’ rig is supplemented and its light articulated by a wide variety of handheld lighting instruments – torches, lanterns and candles – and by the simulated daylight to provide what originally came through the playhouse windows, which have shutters that can be closed to dim the theatre as the historical records suggest was done. The candles would be trimmed or replaced in the interval where necessary. However, the candlelight is not an isolated component of the indoor theatrical experience. There is what I think of as an ecology of lighting of which the candles themselves are just one part. The colours and textures of the painted surfaces are crucial, with a high degree of gilding applied to the cornicing and other carved features designed to catch the light. Costumes too need to be sympathetic to the lighting. In 1625, Sir Francis Bacon wrote of fabrics that ‘the colours that show best by candlelight are white, carnation, and a kind of sea-water-green’ – as can be seen in the work of the 18thcentury English painter Joseph Wright, who made his name with a series of ‘Candle Light’ pictures. These show his especial interest in the contrasts of artificial and natural light, the effects of a single light source and the play of shadows that resulted. Bacon also noted that ‘rich embroidery’ was ‘lost and not discerned’, but recommended the use of ‘oes or spangs [what we would call sequins], as they are of no great cost, so they

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SLL event: Past and Future

Paul Rudy is one of the co-founders of SoraaLaser, which is commercialising a new generation of visible laser sources. He described and demonstrated these pioneering diodes, potentially the next major type of illumination One of Paul Rudy’s co-founders, Dr Shuji Nakamura (who in 2014 was awarded a Nobel Laureate in Physics), invented the blue LED in the 1990s and also, along the way, the violet laser which is made with the same material system based on gallium nitride (GaN). The blue LED combined with phosphor produced the solid state white light source we know now, and the violet low-power laser enabled the entire Blu-ray market. The next step came in moving the violet laser wavelength to the blue, and increasing the power substantially so that now they are able to produce blue laser diodes which, when combined with phosphors to produce white light, have the same kind of lumen output as LED lamps. ‘Unique and beautiful’ is how Rudy describes this new source, a laser diode pumped phosphor, because it can have more than 100 times higher luminance than LEDs. Blue high-power laser diodes have roughly doubled in efficiency over the past five years: high-power blue gallium nitride laser diodes have been combined with special phosphors that can withstand extremely high intensity excitation, while at the same time the use of phosphor-based materials has been substantially improved. The converging results of these advancements has resulted in the production of very high luminance white laser light sources, which have

been initially deployed in automotive lighting, and are now being moved into other application areas. Rudy explained how their work began, when around 2010 they saw the potential of laser pumped phosphor when the first laser phosphor projection display applications were being researched and developed, and which subsequently came on to the market. At that time the phosphor had to be kept moving on a wheel to prevent it burning. Rudy and Nakamura saw that the way forward lay in in enabling static phosphor applications. At the time LEDs were developing and working efficiently and reliably, despite their challenge with fundamental droop. Therefore the advantage of lasers being droop free would have to be offset by making similar progress in their efficiency, power, reliability and cost, hence the need to solve the phosphor dilemma.

‘Blue high-power lasers have doubled in efficiency over the past five years. A laser diode pumped phosphor can have 100 times higher luminance than LEDs’ The level of individual investment needed to make these improvements was daunting. Fortunately between 2011-13 the display market was generating volume in the industry: there was enough critical mass and cycles of learning to allow them to be able to put their calculated improvements into action. In 2013 they spun out a dedicated company, SoraaLaser, to fully work on it. And when Nakamura was awarded the Nobel Prize in 2014, Rudy observes playfully that the professor’s equivalent of going to Disneyworld with his prize was to say in his Nobel speeches: ‘“laser light is next” – and he’s been saying that ever

Comparison of outputs between LEDs and laser light sources




Future: laser vision

SLL event: Past and Future

White laser light SMD (surface-mount device)


since because we were full on committed to the vision in 2013.’ Looking to the future these laser light sources are inevitably going to have a profound impact on the use of lighting and for lighting design. The company envisages the first wave (‘the low hanging fruit’ as Rudy describes it) as literal and straightforward applications of ultra-long spotlights needed for range and distance, overcoming the limitations of LED droop, and being leveraged by the entertainment and architectural lighting industries. He does stress that they see this as an augmentation of the solid state lighting paradigm (in other words, not a replacement for LEDs) to include highly directional sources. Beyond this, he estimates that the second wave would come from the lighting design community understanding the technology, using it and so driving it forward in ways he can only imagine. Regarded as an ideal point source with such

Luminance comparison for a range of different light sources



high luminance, ‘it allows the light to be shaped in dramatic and wonderful ways,’ he says, that have not been previously possible. His company is now looking at ultra-short throw applications where a small pendant on a wall can ‘spray’ several metres of that wall with tiny optics, and how low-cost optical accessories such as holographic diffusers or highly efficient liquid crystal plates can enable very sharp contrasts to create, for example, a highly defined square of light. Rudy likens a lighting designer to an artist whose paintbrush and palette are respectively blue laser and phosphor. SoraaLaser is now prototyping products intended for future commercialisation where the blue laser is incident on a tiny low-cost millimetre MEMS (micro-electro-mechanical systems) mirror which can be pointed, scanned or adjusted to whatever pattern of light one wants to put on the phosphor. That gets imaged out so that in tiny assemblies compatible with today’s LED luminaires, one can now imagine either fully spatially dynamic sources which can be set to provide any static pattern, or little projectional lumination systems inside a luminaire. Using low-cost, single-mirror MEMS, this can be highly reliable and efficient: if you just want one pixel or spot somewhere, you just have to shine the mirror there, without dumping off most of the light as you might with a panel illumination or a matrix of sources that need addressing individually. Indeed Rudy claims that there is so much potential – for instance the integration of sensors, or by developing architectural projection mapping – that he is not daring enough to envision exactly where it will go next, and so they anticipate open-sourcing all this in the future. ‘It will keep us really busy for the coming years,’ he says. ‘Our goal is to provide lighting designers with a wonderful capability and not limit their own imaginations as to what the final sources are. Let the design community run with it.’

LR&T essentials

Preference and perception Iain Carlile singles out four of the latest LR&T papers which look at how colour temperature and lighting method affect our view of space and objects A paper by Stokkermans et al investigates how the method of lighting can affect a person’s impression of a space. Considering brightness and perceived uniformity, an experiment was conducted in which a number of observers viewed high-quality visualisations under controlled conditions. The visualisations were all of the same space but using different styles of lighting (both focused and diffuse). Participants in the experiment assessed the atmosphere for different qualities: cosiness, liveliness, tenseness, and so on. In a second experiment participants evaluated brightness and perceived uniformity. From the results of the investigation it was found that people’s perception of atmosphere can be described as a second-order polynomial as a function of two perceptual light attributes. Huang et al examine the effect of different factors on colour preference, including spectral power distribution (SPD) application, personal colour preferences of observers, cultural difference and gender. LED lighting with differing colour correlated temperature (CCT) values was used to illuminate different objects. Observers were asked to rate the light quality and rank their preference for the different objects under the various lighting conditions. The authors conclude that the light itself, rather than the object being illuminated, is the most important factor when determining which light an observer will prefer. The authors also note that some gamut-based colour metrics correlated with the results of their experiment, observing that colour preference is strongly influenced by colour saturation. Object familiarity was also found to influence colour preference. Also considering colour correlated temperature, Hartstein et al investigated the effects on cognitive task performance in males and females under varying CCTs. An experiment was conducted in which the subjects performed a number of cognitive tasks under both 3500K fluorescent and 5000K LED sources. It was found that under higher CCT illumination females’ (but not males’) reaction time decreased by 10 per cent on a switching task. Conversely, the reaction time of males (but not females) decreased on a go/no-go task, and that no effect was noticed on the mental rotation tasks. It was also found that higher CCT illumination provided improved reaction time on certain attention/executive function tasks, but that improvement is gender specific. A very different investigation into colour temperature was conducted by Jia et al. Their paper looks at a specific application: the illumination of Japanese-style gardens in

The effect of different factors on colour preference (Huang et al)

summer and winter. An analysis was conducted into the influence of a change in CCT on different elements within the scene, including vegetation, water, stone and (warm-toned) structures. Seven different CCTs were applied to an image of the same scene, ranging from 2000K to 10,000K, and observers were asked to note their evaluations (for example, beautiful, attractive, clear, calm, and so on). From an analysis of the results, the authors concluded that in this setting, during summer the optimum CCT values were 2000K for vegetation and stone, 6000K for water and 4000K for structures. In winter for the same scene, the optimum CCT values were 4000K for vegetation and water, and 3000K for stones and structures. Iain Carlile, MSLL, is an associate of DPA Lighting

Lighting Research and Technology: OnlineFirst In advance of being published in the print version of Lighting Research and Technology (LR&T), all papers accepted for publishing are available online. SLL members can gain access to these papers via the society’s website ( Relation between the perceived atmosphere of a lit environment and perceptual attributes of light M Stokkermans, I Vogels, Y de Kort and I Heynderick Light dominates colour preference when correlated colour temperature differs Z Huang, Q Liu, S Westland, MR Pointer, M Ronnier Luo and K Xiao A comparison of the effects of correlated colour temperature and gender on cognitive task performance LE Hartstein, MT Durniak, RF Karlicek Jr and NE Berthier The optimum colour temperature for illumination of Japanese-style gardens in summer and winter D Jia, T Misawa, M Takamatsu and S Hirobayashi




2017 5-7 September Shanghai International Lighting Fair Venue: SNIEC http://shanghai-international-lighting-fair. Mona Lisa, Louvre/Wikimedia Commons

11-12 September Museum Lighting Symposium (Organised by SEAHA and the SLL) Venue: UCL, London WC1 21 September Uchronia (SLL event, focusing on circadian issues) Venue: BDP Lighting, EC1 28 September How to be Brilliant (Organised by the ILP) Venue: Marshalls Design Space, EC1 29 September Night of Heritage Light 3 Location: Oxford 6 October Emergency Lighting to Comply with Fire Safety (CIBSE training course) Venue: CIBSE, Balham High Road, SW12 10 October A Fresh Approach to Interior Lighting Design: an existence-based procedure (SLL LR&T lecture) Speaker: Kit Cuttle Venue: UCL, London 17-19 October Light Middle East (with SLL Ready Steady Light) Venue: Dubai International Convention and Exhibition Centre 19 October How to be Brilliant (Organised by the ILP) Venue: Marshalls Design Space, EC1 27-30 October Hong Kong International Lighting Fair Venue: HK Convention & Exhibition Centre 1 November Fundamental Lighting Course (Organised by the ILP) Venue: Regent House,Rugby

11-12 September: Museum Lighting Symposium, UCL, London

1-4 November Professional Lighting Design Convention (including The Challenge competition) Venue: Palais des Congrès de Paris

Lighting Masterclasses: Masterclass: The Lighting Knowledge Series is kindly sponsored by Fagerhult, Thorn, Trilux and Xicato. For venues and booking details:

15-16 November LuxLive 2017 Venue: London ExCeL 16 November Lux Awards 2017 Venue: InterContinental London – The O2 21 November Lighting Spaces: user wellbeing and performance (Organised by the SLL) Time: 10.30am-12.30 Venue: Olympia, London (Build2Perform, see below) 21-22 November Build2Perform (CIBSE event, formerly Building Performance Conference and Exhibition) Venue: Olympia, London 24 November Lighting: legislation and energy efficiency (CIBSE training course) Venue: CIBSE, Balham High Road, SW12 8 December Lighting Design: principles and application (CIBSE training course) Venue: CIBSE, Balham High Road, SW12

LET Diploma: advanced qualification by distance learning. Details from or email CIBSE Training: various courses across the whole spectrum of lighting and at sites across the UK. Full details at www.cibse. org/training-events/cibse-cpd-training LIA courses: details from Sarah Lavell, 01952 290905, or email For up-to-date information follow us on Twitter @sll100

SLL sept:oct 17