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Newsletter Volume 10. Issue 2. Mar/Apr 2017

The Society of Light and Lighting

Part of the Chartered Institution of Building Services Engineers

SHADES OF INFLUENCE Prof Stephen Westland on current research into colour




Secretary Brendan Keely MSLL 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 Wiebke Friedewald Mark Ingram MSLL Stewart Langdown MSLL Linda Salamoun 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 3 2017 is 24 March 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

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)

Produced by

LATEST SLL Lighting Guide 14: Control of Electric Lighting (2016)


Guide to Limiting Obtrusive Light (2012) Guide to the Lighting of Licensed Premises (2011)

Printed in UK


The phrase ‘alternative facts’ has rapidly entered the lexicon since it was coined in January by Kellyanne Conway, US counsellor to President Trump, to finesse a falsehood about attendance at the inauguration. It is yet another example of an increasingly pervasive Newspeak. In a different and specialised context, lighting is one of those areas that arguably has been subject to alternative facts or, at the very least, misguided and unsubstantiated half-truths. On the one hand there is the good old tabloid scare story. Google the words ‘LED danger’ and you’ll come up with a raft of dire warnings, including the headline ‘Do environmentally friendly LEDs cause blindness?’ (the Daily Mail, naturally). And judging by a range of reports over the years, it seems that

LEDs can do everything from causing cancer to curing it. At the less hysterical end of the spectrum, and even among the lighting cognoscenti, there is a fair degree of acceptance of recently discovered attributes of light. That blue light (or cool white light) creates greater alertness and productivity, for instance, with biodynamic systems being installed in the more prestigious workplaces. Blue light also became much publicised a few years back as a factor in suicide prevention, with railway stations in Tokyo and Gatwick implementing the strategy. Red light, meanwhile, apparently increases blood pressure. Prof Stephen Westland, who writes in this issue about his current research into the effect of coloured light on alertness and impulsivity (How does chromaticity colour our life? p10), is concerned that there is a danger of jumping the gun with coloured lighting. He isn’t saying these theories aren’t true, he’s just saying they still haven’t been proven beyond doubt. ‘Some research has been carried out and suggests that there are measurable and robust effects,’ writes Westland. ‘However, some of the research is flawed and the need for further studies in this field has probably never been greater than it is now.’

Secretary’s column

The subscription renewal notifications for 2017 have now been sent out. Being a member of the society will help you demonstrate your competence to your clients and peers The new Masterclass: Lighting Knowledge Series – Human Responses to Light has been very well received by the delegates in Dublin, Leeds, Birmingham and Manchester. Bookings are already being taken for the Bristol, Glasgow and London events in March, April and May. . Congratulations to Jeff Shaw and his student Marina Lodl, who emerged as a finalist from Round III of The Challenge speaker competition held at Brunel University last month. They will join the other lucky winners (six teams in all) at the finals in November at the Professional Lighting Design Convention (PLD-C) in Paris. We are delighted again to support the PLD-C competition and convention as Knowledge Partner. And finally, the Annual Awards Evening, Presidential Address and AGM will take place in London on 25 May. We hope many of you will be able to join us for an evening celebrating the new society’s president, Richard Caple, and our award winners.

Editorial 2 Secretary’s column


News 4 Glow with the flow 5 Based on her winning paper, YLOTY Sofia Tolia looks at taking a different approach to variable lighting levels for highways Body of evidence 8 Summarising his presentation for the latest Masterclass series, Chris Wilkes looks at human physiological responses How does chromaticity colour our life? Professor Stephen Westland outlines his current research into the effect of light on alertness and impulsivity


Case for an expert eye 2 Paul Ruffles concludes his glimpse into the world of the lighting investigator


The eyes have it Glare and visual fatigue are among recent LR&T topics singled out by Iain Carlile


Cover project 15 Folded Light by Carpenter Lowings at 8 Finsbury Circus

Photography: Timothy Soar

We are getting excited about the 15th annual Ready Steady Light competition due to take place on 21 March, one of the best days of the year. The winners’ trophies for the Artistic, Technical and Peer awards have been ordered and delivered – will you be one of the recipients? We’re teaming up with Rose Bruford College again and only have 14 sites to work with – that means a maximum of 14 teams, and as we’ve not got many team places left, please do get in touch quickly to secure your place. Rose Bruford will also host Junior Ready Steady Light, which will take place on 18 March. If you are involved with a school or know of a school with 11-16-year-olds that would like to take part then please do let us know. The subscription renewal notifications for 2017 have been sent out and we encourage all to continue to enjoy the benefits of the society and CIBSE. If you are an affiliate or associate member of the society and have the right amount of experience, then we also encourage you to upgrade your membership to acknowledge your lighting experience, skills and competence. There are many routes from affiliate member through to associate member and then member. For example, if you have five years’ experience in lighting you could become an associate member simply by completing a straightforward form and a Professional Review Statement, which is two to three A4 pages describing your work and challenges in light and lighting. If you have 10 years’ experience in lighting you could become a member, again simply by completing a simple form and a Professional Review Statement. With associate member and member grades of the society you can use the post-nominal letters AMSLL and MSLL respectively in your signatures, curriculum vitae, business cards and

project bids, signifying that you have demonstrated your competence in your field of lighting and been accepted by this leading professional body. If you have had an education in light and lighting then the required duration of your experience is reduced. For instance, if you have passed the Lighting Education Trust Diploma, have three LIA Advanced Certificates or a Masters in Lighting, you only need two years’ experience to move from affiliate to associate member; to upgrade to member it would be five years. Becoming an associate member (AMSLL) or member (MSLL) will add another £10 and £20 respectively to your annual subscription. The information is on the society’s website but please do contact us should you wish to upgrade your membership. We are happy to talk anyone through the options.



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



Bursary available with double original funding The Jean Heap Bursary is now open for applications with a £4000 fund, twice the initial amount following a decision not to award the research grant in 2016. It should revert to £2000 next year. Launched in 2014 to honour former president Jean Heap (pictured), the bursary is for a lighting study or piece of research designed to benefit the industry and SLL members. It is open to everyone with an interest in lighting. Applicants must state how the study would benefit the industry, and show how the funds would add to the research. Deadline for applications is 30 April.

Dimming has grass roots impact


Dimming and switch-off can be used to reduce the impact of LED street lighting on the environment, according to new research by the University of Exeter. The study found that predatory spiders and beetles were drawn to grassland patches lit by LED lighting at night, but the number of species affected was markedly reduced when the lights were dimmed by 50 per cent and switched off between midnight and 4am. ‘Without appropriate management, our results suggest that the growing use of LED lighting will have impacts on the abundance of predatory invertebrates, potentially leading to knock-on effects for other species in grassland food-webs,’ said Dr Thomas Davies of Exeter’s Environment and Sustainability Institute. ‘Our research shows that local authorities might be able to manage

The Lighting Industry Association has received the award for Best Construction Industry Trade Association, UK, in the 2016 Facilities Management Awards, organised by Build Magazine. The LIA Certificate has been revamped for 2017. It will now involve a two-day Lighting Fundamentals course, providing a basic grounding in the principles of light and lighting.There will also be a one-day session on Light Sources and Luminaires and a further one-day course, Lighting Design. The course can be taken over consecutive days or modules can be taken separately. The SLL Membership Panel will now meet every two months rather than quarterly as before. The meetings will be held online in order to give quicker responses to applicants.

LED lighting in a way that reduces its environmental impacts. We now need to establish whether this is the case for a greater variety of species.’ While it is LED lighting involved in the study, Davies points out that it is not being singled out in comparison with traditional sources. The aim was to conduct the research with what is becoming the most ubiquitous source. ‘Given that LED lighting will be the dominant light type by 2020, it makes sense to evaluate how this lighting can best be managed to avoid deleterious ecological affects,’ said Davies. ‘Comparisons with other light sources are irrelevant in this context.’

On the lighter side... Shooting for the stars is a cliche when it comes to describing ambition, but is remarkably apt for Dr Lena Okajima. She has founded a business, ALE, to create artificial meteorites for a light show in space. ‘This type of project mixes astronomy and the entertainment business,’ she says. The goal is for it to be fully working for the 2020 Tokyo Olympics.



The process involves firing some 1000 2cm-diameter chemical pellets from a cuboid satellite 500km above the Earth. With varying compositions, each will produce a different colour or brightness. Lasting four years, the satellite also has a down-to-earth purpose. ‘The resulting funds will further advance fundamental scientific research,’ says Dr Okajima.

Events:YLOTY Masterclass WINNER 2013/14 2016

Glow with the flow

Based on her winning paper, Young Lighter of the Year Sofia Tolia looks at taking a different approach to variable lighting levels for highways

Theoretical background Designing a road lighting scheme in accordance with the European Standard (EN 13201:2004 1-4 and EN 5489-1:2013) can lead to some energy savings because in many cases the existing luminaires provide excessive lighting levels. However, the use of different control strategies could ensure energy savings beyond this. Traditionally in road lighting the luminaires are switched on/ off manually or automatically by photocells and/or timers which are programmed according to the sunset and sunrise hours. Therefore, lamps are burning at full power during the whole night and lighting intensity is often excessive when traffic flow is low or under extreme weather conditions such as snow. In some cases, in order to consume less energy, every second luminaire is switched off after a specific time during the night. However, this results in poor luminance uniformity and therefore poor driving conditions. Therefore the application of different energy-saving strategies, such as the variation of lighting levels on all classifications of road depending on usage at any time, is crucial. The purpose of my report was to examine the accuracy of the calculation method for the variable lighting classes that is briefly described in BS5489-1:2013 Code of Practice for the Design of Road Lighting, and further analysed in TR27 Code of Practice for Variable Lighting Levels for Highways. Current state-of-the-art Variable lighting is often referred to as dimming, but more appropriately it is lighting to the correct lighting class in order to meet specific road parameters at a particular time. As highlighted in the BS5489-1:2013 Code of Practice for the Design of Road Lighting, the significant reductions in traffic flow during the night-time could result in the reduction of the applied lighting levels, given that all the other parameters that define the road classification remain the same (type of road, crime

risk, weather conditions, presence of conflict areas, parked vehicles). However, the lighting classification for the traffic routes is based on daily traffic flow (ADT) with the transition values being 7000, 15,000 and 40,000 vehicles a day. In order to examine the application of the variable road classifications, the actual hourly traffic flow needs to be considered. As properly detailed in TR27, the ADT transition levels should be scaled down to hourly transition levels and therefore the maximum hourly value (peak) is related to the daily sum. The rationale behind this decision is that using the maximum values for the derivation of the scheme would serve even the most traffic-demanding days and therefore would take into consideration any possible variation in the traffic flow. At this stage of the calculation procedure, TR27 and BS5489-1: 2013 recommend that the peak traffic flow is typically 10 per cent of ADT for rural areas and 12 per cent of ADT for urban areas. A novel calculation approach The latter assumption is looked at in this study in order to determine the accuracy of the calculation procedure. Instead of considering a fixed percentage of the ADT as the hourly peak traffic flow, a further data analysis is recommended. Given the hourly traffic flow data for each month, the whole range of the maximum traffic flow within the month can be obtained by applying simple statistical methods. The first step is to analyse the daily traffic flow, by calculating the average value and the standard deviation using data from all the months. Following this calculation, the range of the traffic flow within these months can be obtained and at this stage, the accurate maximum hourly value (peak) can be related to the daily sum and not the percentage recommended by TR27. The recommended calculation procedure and the formulas used are illustrated in Figure 1 (below).

Fig 1: recommended calculation procedure for the two thresholds and formulas



Nowadays we expect much more from outdoor lighting than the possibility to see at night. Road lighting has become a necessary tool for reducing the number of night-time road traffic accidents, improving the visual comfort of drivers, for its potential to increase the night-time traffic capacity of a given road and the reduction of criminality. At the same time, the global climate shift, the rising energy costs and the reduction of CO2 emissions are all major issues that the world faces today. Lighting currently accounts for 19 per cent of the global electricity consumption and around eight per cent of that is being used for outdoor lighting. A competent lighting designer has therefore two main objectives to meet on every design: satisfy the users’ needs in accordance with the relevant lighting design standards and provide energy efficient lighting schemes.




Case study The proposed method was examined in a case study on several roads around the port of Piraeus in Greece. For more accurate results, the traffic flow data was analysed throughout three representative months of the year: March or September, being closer to the equinox; December, which is close to the winter solstice, and July for the summer solstice. It should be noted that the difference in the data between weekdays and weekends was remarkable. Therefore, all the calculations were performed separately for weekdays and weekends. Figure 2 (below) illustrates a representative example of this difference, showing the actual traffic flow values for each day for one week within a 24-hour period. The traffic flow and the speed were

Fig 2: graphical representation of the traffic flow during one week

monitored in 12 different measuring positions along the port of Piraeus, and the lighting classifications, derived from analysing all the relevant parameters, are shown in Figure 3 (below).

Further analysis and calculations After classifying all the roads and determining the new variable lighting classes, the next step was to calculate the possible dimming levels for every hour of the day. For this calculation, a module in Visual Basic was created. Two types of control systems were examined in this study: a time-schedule-based control system, where the light output can be adjusted to different dimming levels according to a preset time schedule, and a more complicated control system that uses traffic counts to get real-time information of the traffic flow, adjusting dimming levels to the flow measured. The hours for each level of dimming were counted both for the time-schedulebased dimming and for the real-time/dynamic dimming. In both cases, for more accurate results, the fact that fittings are turned on half an hour after sunset and off half an hour before sunrise was taken into consideration. This resulted in the calculation of the exact hours of dimming. The exact hours of sunrise and sunset were incorporated into the VB module. The final stage was to identify the luminance levels for each lighting class according to EN BS 13201/2004:2. This resulted in the calculation of the exact dimming percentages. It was estimated that the reduction percentage of watts consumed was approximately equal to the reduction percentage of the luminance because the installed luminaires in these roads are using LED technology. Results and discussion As illustrated in Figure 4 (above right), there is a significant difference in the calculated thresholds. With the TR27 method the first dimming value should be applied to luminaires four hours earlier than the proposed method. This would result in roads being underlit for a significant amount of hours in relation to the hourly traffic flow proposed method.

Fig 3: lighting classification of the roads around the port of Piraeus




Fig 4: comparison between the proposed calculation method and the TR27 calculation method

Having identified the new thresholds for the transition levels and the variable lighting classes for each examined road, the exact dimming regimes were calculated, based on the proposed luminance levels in accordance with EN BS 13201/2004:2. Figure 5 (below) illustrates a representative example of a timescheduled dimming profile.

(peak) is significantly lower compared to the 10 or 12 per cent recommended by TR27. Even though this reduction in the switching transition levels would result in less energy savings, it provides greater accuracy in the calculation of the dimming values and therefore more safety for the road users, as the road classification is in absolute accordance with the lighting classes of British and European Standards. On the roads along the port of Piraeus, it is observed that the levels of the traffic flow are reduced significantly and the application of a lighting control strategy could save a significant amount of energy. A time-scheduled dimming strategy based on the real traffic flow data throughout the year could provide 29 per cent overall energy savings. Moreover, the application of a control strategy that could make use of the real-time information of the traffic flow at all times could offer an overall 32 per cent reduction in energy. However, prior to considering the application of the second diming strategy, an extensive study of the cost of installation of the required equipment should be conducted to find out the payback period in comparison to the further energy savings that have been calculated within the framework of this paper. Sofia Tolia delivered her paper, Variable Lighting Levels for Highways: A Different Approach, during the LuxLive exhibition at London’s ExCeL in November. For the full version, go to:,-a-differentapproach.pdf.aspx

Fig 5: dimming profile for the luminaires of a representative road with the time-scheduled control strategy

References (numbered in full paper) Moving forward, the installation of some additional equipment that could connect the control system with the real-time counts of the traffic flow on each road could offer an even more accurate dimming profile. Figure 6 (below) illustrates such a dimming profile for the same representative road.

Fig 6: dimming profile for the luminaires of a representative road with the real-time-data control strategy

Comparing the two strategies, the additional energy savings when applying the second strategy amount to three per cent. Conclusion and future considerations The results and analysis provide a clear understanding of the benefits of a dimming strategy for a road lighting scheme. As expected, the outcome of the study in relation to the switching transition levels for the variable classification was that the calculated percentage of the ADT for the maximum hourly value

Peter Raynham. An examination of the fundamentals of road lighting for pedestrians and drivers. London: Lighting Research and Technology, 2004, Vol. 36, pp 307-316. International Energy Agency. Light's Labour’s Lost – Policies for Energy-Efficient Lighting, Paris: IEA Publications, 2006. Richard Black. Lighting the key to energy saving. BBC News. [Online] [Cited: 16 August 2013] Aleksanteri Ekrias. Development and enhancement of road lighting principles, Aalto University of science and technology, 2010 BS5489-1:2013, European Standard. Code of Practice for the Design of Road Lighting TR27, Technical Report, Code of Practice for Variable Lighting Levels for Highways, Institution of Lighting Professionals LIping Guo. Intelligent road lighting control systems – Experiences, measurements and lighting control strategies. Espoo, Finland: Helsinki University of Technology, Department of electronics, Lighting Unit, 2008. N v Tien, Y Unhavaithaya, N n Dinh. Lighting control in street lighting – an overview of the state of art in technology and application. Right Light 6 International Conference on Energy-Efficient Lighting, 2005.



SLL Masterclass 2016-17

Body of evidence

Summarising his presentation for the latest Masterclass Lighting Knowledge series, Chris Wilkes of Holophane looks at human physiological responses There are many well-known effects of lighting on the natural world around us – and also many unknown effects. Probably the most cited example in this respect is bats because if you have been involved with exterior lighting in the UK, there is a very high chance that you have had to deal with, or at least be aware of, lighting for bats, and the various regulations by region associated with them. Birds, amphibians and invertebrates are all subject to behavioural change as a result of excessive or inappropriate light. (A study of grassland invertebrates reported on p4 is just the latest to find evidence of this.)



Even plants must also be considered.At a recent exhibition, I had the opportunity to spend some time with a plant biologist, who is one of the most experienced people I have talked to on the effect of lighting on plants. (Two key takeaways for me were that when it comes to understanding the effect of light on plants we have a lot to thank the drug industry for because that is where the money is. And that almost everything we have learnt has been done by trial and error. A bit of blue light here, a bit of red light there, and see what happens...) Now, if we know that light and lighting can affect nature then it is not a large leap to accepting it can affect us as humans

SLL Masterclass 2016-17

(assuming we didn’t already know). It does so in a myriad ways, both positively and negatively, as the following few examples demonstrate: Sunburn Photoconjuntivitis Ageing of our skin Vitamin D production Biological rhythms Phototherapy With the lighting industry having firmly embraced LEDs, the possible negative effects of solid state lighting on human health and wellbeing are at the forefront of discussion. We are hearing about blue light hazard, circadian rhythms and flicker among other issues, as if they were new phenomena. Of course they are not. It just seems that because of the relative newness of LEDs we are all talking about them again. There are a number of reasons why this might be so. New technology is always a bit scary – and as a general rule we don’t like too much change. Blue LEDs are also widely used as a base on to which we introduce phosphor to create white light – blue light can be damaging, ergo LEDs could be considered dangerous. As we know, there is much research being carried out globally around these potential effects. This is not always coordinated, which means we will not get to the ‘solution’ as quickly as we might think we should, but bodies such as CIBSE and the SLL are funding targeted research which should help. Involved in this research are not just people within the lighting profession; medical and academic bodies are also engaged, lending their particular perspective and expertise so that eventually we will build up a more rounded picture. A prime example is the research that was carried out by Public Health England and published last year. PHE, responsible for providing advice to government, professional bodies and the public on optical radiation safety, was commissioned by the SLL and CIBSE to review the impact of LED lighting on humans. This study involved a review of the emissions from domestic, office and street lighting. The report broadly dismissed the blue light hazard. ‘A number of press reports have claimed that LED sources are potentially harmful,’ said John O’Hagan in a summary for the Newsletter (January/ February 2016), ‘but scrutiny of the claims usually shows that the exposures are under highly unrealistic exposure situations.’ I would encourage you to download a copy from the website ( and have a read. This is a document where we as a lighting industry have commissioned independent experts to research key topics for us and give us the best possible current information on how lighting can affect us. We have asked the question, let’s listen to the answer. Much of the research currently being undertaken, and one of the more widely discussed areas of the relationship humans have to light, centres on the non-visual aspect – melatonin production and circadian rhythms. I don’t explore those aspects of the discussion as they are dealt with in more depth in other Masterclass presentations. Instead my presentation is concerned with some of our direct responses to light and how that affects, or should affect, the lighting schemes we create. As humans we each respond in different ways to light, and our individual responses vary

Blue light hazard is among several topics that has become widely discussed again with the spread of LEDs

according to a number of factors. For example, a young adult eye pupil will dilate to its largest size – a diameter of around 8mm – to let the maximum amount of light on to our retina at low levels of luminance, while at the other end of the scale the same pupil will contract to roughly 2-3mm in diameter. As we get older we tend to have smaller pupils under comparable conditions, making it harder for us to see without more light. This will be one of the factors that leads to differences in recommended light levels. If a space contains a majority of people under the age of 25, the level might be 200 lux, but that same space for people aged over the age of 65 would have a recommended light level of 800 lux, in other words four times more light (IESNA hand book 10th Edition). But of course the eye is just our personal light sensor; the majority of the visual system resides in the brain, which interprets what we see. Where lighting is concerned, what we experience can be a matter of perception rather than reality. For instance, if we dim a lighting installation to 10 per cent, we nevertheless perceive levels to be 32 per cent of the original. What is clear is that this is an immensely complex subject and one we are continually learning about. I have been in the lighting industry for more than 13 years, most of that time spent in or around lighting laboratories. I like things that can be quantified and measured, and then clear metrics developed for repeatable use. Much of lighting revolves around metrics, of course. However, what is ultimately more important is not numbers but people – the users of the space and how they use it. Human response and reaction can be difficult to measure. As well as the issues of individuality I have mentioned, much user experience is difficult to quantify as our response to a space is heavily related to factors such as mood and level of alertness or fatigue. How we use a space from one day/week/month to the next can be very different – what is clear is that it is not something that can be boiled down to a simple equation. The Public Health England report can be viewed at detail?id=a0q20000008I6z6 Physiological Responses to Light is one of the four presentations, plus guest speaker’s address, that will be delivered at the one-day Masterclass Lighting Knowledge Series: Human Responses to Light. The remaining Masterclasses will be in Bristol (30 March), Glasgow (27 April) and London (18 May) @sll100



How does chromaticity colour our life?

Professor Stephen Westland of Leeds University outlines his current research into the effect of light on alertness and impulsivity

The increased affordability and efficiency of colour solid-state lighting is generating huge opportunities for the use of colour in the way we illuminate our spaces for work, home and play. To what extent can the colour of our environment be used to affect productivity, wellbeing or even creativity? The answers to these questions are surprisingly not clear cut. Some research has been carried out and suggests that there are measurable and robust effects; however, some of the research is flawed and the need for further studies in this field has probably never been greater than it is now. Although, for example, the internet is awash with bold statements such as that red light increases blood pressure and blue or green light decrease it, there are few studies that genuinely support this claim. It is difficult, for example, to find strong academic evidence to support the use of blue lights to reduce suicides (and anti-social behaviour) in public places despite their installation on train platforms in Tokyo1 (most



notably) and, more recently, by Network Rail at Gatwick airport. Research in the Experience Design research group at the University of Leeds is attempting to answer some of the questions about the effect of colour and light that could lead to better design of lighting in homes, workplaces and public spaces. The research uses an LED room-lighting system that incorporates 11 different coloured LEDs that can enable spectral, rather than colorimetric, specification of light output. This spectrally defined coloured lighting has been used by PhD students at the university to explore the effect of colour on alertness, impulsivity and creativity, and four of these studies are briefly described in this article. There are a number of ways to measure alertness, including increased blood pressure and heart rate, reduce alpha power (obtained from EEG recordings), self-reporting through questionnaires, and performance in various tasks. In one study the effect of the colour background on a computer display was varied as participants undertook a range of cognitive tasks. Error rates were significantly lower for red and purple backgrounds and higher for yellow backgrounds in particular. Meanwhile, response rates were also faster for the red and purple backgrounds. The red and purple backgrounds therefore resulted in both enhanced performance at the cognitive tasks, and higher alertness. Other studies, often using short bursts of intense illumination, have shown that blue light increases alertness in the evening and a mechanism that involves suppression of melatonin by activation of intrinsically photosensitive Retinal Ganglion Cells (ipRGC) is often supposed2. However, part of the difficulty here is that light reaching the retina can affect the brain through multiple pathways, and the time of day and the duration of the light stimulus are just two factors that might modify any effects3. Indeed, even though the ipRGCs are implicated in the observation that short-wavelength light suppresses melatonin, recent research has found that both blue and red light can enhance alertness at night4. Furthermore, data now suggest that different pathways from the eye to the brain regulate sleep and increase arousal5. The data at Leeds suggest that red light can have a positive effect on alertness during the day. A second study that explicitly


measured the effect of lighting on heart rate and blood pressure found that red light increased heart rate, as well as systolic and diastolic blood pressure compared with green, blue and white light conditions6. A study into the effect of lighting on impulsivity is underway that uses a triangulation of different research methods. Three measures for impulsivity are being used: first, self-reporting though the use of questionnaires; second, measurement of alpha power using EEG, and, third, performance in several tasks. In order to use questionnaires to assess how impulsive participants feel it is important to distinguish between their state and trait. Participants may vary in how impulsive they are in terms of their character type or their trait; however, the effect of light is much more likely to affect their state (which is how impulsive they feel ‘now’). A number of questionnaires have been reported in the literature as being able to measure impulsivity state, including the Momentary Impulsivity Scale7 and the Assessing Mood in Daily Life Scale8. Results from the Leeds study using these scales suggest that red light has the strongest positive effect on impulsivity; participants under the red light scored as more impulsive than when under green, blue, yellow or white lights. A final study at Leeds in conjunction with Zhejiang University in China looked at how dynamic lighting can affect alertness. Dynamic light varies the colour temperature and intensity of lighting to affect wellbeing and performance9. Measurements of alpha power from EEG recordings were lower (suggesting increased alertness) when participants spent time under lighting that varied between 6000K and 1200K over two or four hours when compared with a similar intensity of static light at 9000K. Much more work is needed to confirm these effects and it is likely that results will sometimes seem contradictory. There are several reasons for this. First, there is the complication that the pathways from retina to brain are complex and possibly interact depending upon conditions. Secondly, the effects are sometimes small and noise in the measurement is high, which requires large studies with high numbers of participants. Thirdly, some of the effects we would like to measure, such as impulsivity, performance and creativity, are complex and these concepts may themselves need refining to make sense of experimental data. Professor Westland is chair of colour science and technology at the School of Design, University of Leeds. He was the guest speaker at the SLL Masterclass in Manchester last month

Thouslite Lighting System

References 1 Matsubayashi T, Sawada Y and Ueda M (2014). Does the installation of blue lights on train platforms shift suicide to another station?: Evidence from Japan, Journal of Affective Disorders, 169, 57 2 Revell VL, Arendt J, Fogg LF and Skene DJ (2006). Alerting effects of light are sensitive to very short wavelengths, Neuroscience Letters, 399 (1-2), 96 3 Anderson M, Mardaljevic J and Lockley SW (2012). A framework for predicting the non-visual effects of daylight – Part I: photobiology-based model , Lighting Research and Technology, 44 (1), 37 4 Figueiro MG, Bierman A, Plitnick B and Rea MS (2009). Preliminary evidence that both blue and red light can induce alertness at night, BMC Neuroscience, 10 (1), 105 5 Pilorz V, Tam SK, Hughes S, Pothecary CA, Jagannath A, Hankins MW, Bannerman DM, Lightman SL, Vyazovskiy VV, Nolan PM and Foster RG (2016). Melanopsin regulates both sleep-promoting and arousal-promoting responses to light, PLoS Biol, 14 (6), e1002482 6 Lee S and Westland S (2015). Does colour really affect pulse rate and blood pressure? Proceedings of the Midterm Meeting of the International Color Association, Tokyo, 1118 7 Tomko RL, Solhan MB, Carpenter RW, Brown WC, Jahng S, Wood PK and Trull TJ (2014). Measuring impulsivity in daily life: the momentary impulsivity scale, 8 Psychological Assessment, 26 (2), 339 Wilhelm P and Schoebi D (2007). Assessing mood in daily life, European Journal of Psychological Assessment, 23 (4), 258 9 De Kort YA and Smolders KC (2010). Effects of dynamic lighting on office workers: First results of a field study with monthly alternating settings. Lighting Research and Technology, 42 (3), 345.

Effect of coloured light on heart rate (PR) and blood pressure (BP).



Professional insight

Case for an expert eye Concluding his two-part article on lighting investigation, Paul Ruffles looks at patent issues, exterior lighting – and the qualities and qualifications it takes to do a job where CSI meets Sherlock Holmes In the last issue, I looked at various areas where a technical investigator or expert witness might be called in. To conclude, I will look at two final areas, patent or design infringement, and exterior lighting, and also outline what requirements and qualifications are needed to work in this field. Patent or design infringement This is a contentious area – two manufacturers arguing over whether one party’s product is too similar to the others. Of course sometimes one manufacturer does deliberately copy another’s product, but often it is a case of something being similar by coincidence. With so many slight variations on a limited number of themes in the luminaire market, this can be a difficult issue to determine. You need to compare characteristics – these may be the physical form of the product, the materials used in its construction, the electronics or mechanisms used inside it, the light distribution from it or possibly some combination of all of these. To accurately determine such issues, you need to compare the characteristics of the two products not just with each other, but with other similar products in the market. In this way you can better inform the court of how similar they are to each other in the context of a range of similar products in their category. In cases where the independent expert finds that the product similarities are due to ‘simultaneous development’ rather than direct copying, they can give this dispassionate view to the aggrieved party so perhaps avoiding the need for an expensive and unnecessary court case. Outside problems Exterior lighting faults can, of course, be similar to those found with interior lighting, but they also have that exciting added ingredient – water. Sealed lights are only truly watertight when installed and operated correctly. Sometimes the cable isn’t sealed into the gland properly; sometimes the luminaire is under stress, forcing a joint open, and sometimes the maintenance people have relamped and not bothered with the complicated process of resealing the access hatch or front glass. Because the lights heat up when on and cool down when turned off, the air in sealed fittings expands then contracts as it cools down – any water near joints then comes under pressure to be sucked into the luminaire.



Exterior lighting faults can, of course, be similar to those found with interior lighting, but they also have that exciting added ingredient – water A typical case involved the failure of sealed flat panels set flush in the surface of a public square. These contained LEDs around the edge of a frosted panel with some of the panels having water from an in-ground water feature flowing over them. I won’t go into the details of this one, suffice to say to anyone thinking of designing or specifying a 600mm square in-ground panel that can stay waterproof when cycling on and off, under rain and full sun, with people, trollies and, probably, the occasional van, passing over them – it’s not easy. A more extreme case involved luminaires along the side of a bridge failing to work as intended. Here you not only had the normal problems with rain, but also vibration from vehicles, wind and slightly salty air from an estuary. However, after a detailed investigation it turned out to be low winter temperatures that were causing the problem. Neither the lamps nor the dimmable ballasts were able to cope in winter leading to unreliable operation and stress on components. As is quite

Professional insight

often the case once I looked at the paper trail (or email trail these days) it became apparent that the specification of the lamps and gear, which was a special, had not been completely clear. Not all information was passed clearly between the specifiers and the manufacturers, and some of the discussions were verbal and not confirmed in writing. A slightly different sort of investigation was triggered a few years back by a child falling on to a recessed uplight in a park and burning themselves. The owners immediately turned off the lights, which somewhat ruined their illumination of the trees in the park, and they got me in to determine if the luminaires were safe to have been installed in a public area. To determine this involved the study of thermal conductivity of glass and various metals, as well as delving into medical texts to understand the interesting relationship between contact time and temperature that leads to a skin burn. The outcome was that they were far too hot to be allowed to be turned back on. This was one of the cases that led to standards being changed and low temperature front glasses being specified on accessible in-ground luminaires. As with interior projects you also get cases where someone believes that they have fallen due to inadequate light on a path or similar walkway. It may seem rather strange that while a person can happily wander along a pebbly beach under moonlight they can then walk into their hotel gardens and complain of inadequate light when they stumble on the well-laid, flat path. But of course the beach is unowned land and the garden path is someone’s responsibility. In these sorts of cases there is rarely someone on hand at the time of the fall with a recently calibrated light meter in their pocket, so you need to try to establish the likely light level on the path several months down the line when you have been asked to investigate by one of the parties involved in what is now an insurance claim. To do so you can measure the light level on the path now, but you need to check whether the owner has quickly cleaned and relamped the lights in anticipation of your visit and, if so, attempt to calculate the impact of this. You will also need to determine the latitude and longitude of the location to calculate when astronomical and nautical dusk occurred around the time of the injury, to see what sky light there may have been. You may also have to research the weather conditions at the time to see what cloud cover there was to try to estimate sky glow from both sky light and light pollution – all very nebulous. At best you will be able to determine a rough range of likely lighting levels on the path at the time of the fall.

likely in the case and a good general technical knowledge in case surrounding problems emerge. I’ve had cases where I’ve had to research material degradation under low temperatures, mechanical stress on cables and electro-magnetically induced currents, as unexpected side issues. When considering whether to promote yourself as an expert witness you have to remember the ‘witness’ part of that title – you may need to stand up in a court and defend your opinion. There are two important criteria here: the ability to present and defend your investigation clearly and precisely, and the ability to be cross-examined by someone who may be not only trying to pick fault with your tests or analysis, but also to question your ability or qualifications. For me that hasn’t been a problem: my degree was in electrical and electronic engineering; I’ve sat on the SLL’s technical committee for 30 years and chaired it on two occasions; I was a member of British Standard Committee EL/001 Lighting applications for 20 years and have sat on many other technical and standards committees. This gives me the requisite ‘court clout’ in case the barristers start playing the ‘my expert is bigger than your expert’ game – sad but true. You also must remember that regardless of who is paying your fee you are appointed by the court to assist it in determining the case – you must remain impartial.

I have the requisite ‘court clout’ in case the barristers start playing the ‘my expert is bigger than your expert’ game

Competence To get involved in the area of technical investigation you will, of course, need to be ‘qualified’ in the area under investigation. This means a good knowledge of the direct technical issues @sll100


LR&T essentials

The eyes have it

Glare caused by coloured LEDs and visual fatigue from VDTs are among the topics of recently published papers singled out by Iain Carlile In the third part of their papers on glare assessment, Yang, Luo and Huang investigate the assessment of discomfort glare caused by coloured LEDs. The results from their experiment showed that coloured light LEDs caused greater discomfort glare than white light LEDs at the same luminance. Blue LEDs resulted in the strongest glare perception. The authors also found that there was a strong correlation between brightness perception and glare perception, suggesting brightness models may be a suitable approach to predicting glare. In their paper, Wang et al present a model for assessing visual fatigue in people using visual display terminals (VDT) under LED lighting conditions for extended periods of time. The model was constructed from data derived from 20 participants over a period of eight hours of work at a VDT; five opthalmological parameters and three physiological signals were used. The resultant model allows visual fatigue to be assessed and predicted by short-term evaluation rather than prolonged long-term measurement. The authors also concluded that the absolute level of visual fatigue under LED light sources was small while working at a VDT. Pedersen and Johansson’s paper explores the dimming of lighting to pedestrian pathways and the effect it has on the pedestrians in terms of walking speed, legibility and perception. In an indoor, full-scale mock-up of a 19m-long pathway, it was found that participants in the experiment walked significantly slower when the lighting was dimmed, even once the lighting was increased to full illuminance. Larger differences between the dimmed state and full illuminance resulted in slower walking speeds, both before and after the increase in light. It was also observed that legibility decreased with dimming – the greater the difference between the dimmed and full state, the stronger the reported reaction from the experiment’s participants. The results indicate that changes in illuminance affect walking speed, and that legibility and perception are affected by the overall lighting design of pathways rather than dimming as such. The authors note that using dimmability as a way to save energy needs to be carefully considered in the design of pedestrian pathways if it is not to have a detrimental effect on pedestrians. Finally Rea and Figueiro examine the impact of retinal light exposure on the regulation and disruption of human circadian rhythms. They consider the adoption of a new metric characterising how light affects the human circadian system as a way to quantify light in architectural spaces. The authors encourage open discussions between manufacturing, research and application stakeholders about characterising light for the circadian system in various applications. They note that, while not everything is known about the effect of light on the circadian system, the science is now suitably mature for lighting



Experiment set-up for assessing glare from coloured LEDs (Assessing glare, Part 3. Yang et al)

stakeholders to make conscious, informed and documented decisions over the approach to take. Ultimately they ask if the approach should be based on conventional photometry methods with post hoc ‘correction’ factors guided by scientific evidence, or if a completely new approach to calculation and measurement of light is needed based on the scientific evidence. 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. Members of the society can gain access to these papers via the SLL website ( Light as a circadian stimulus for architectural lighting MS Rea and MG Figueiro Assessing glare, Part 3: Glare sources having different colours Y Yang, M Ronnier Luo and WJ Huang A model for evaluating visual fatigue under LED light sources based on long-term visual display terminal work Y Wang, X Zhong, Y Tu, L Wang, Y Zhang, T Wang, C Zhang and W Zhou Dynamic pedestrian lighting: Effects on walking speed, legibility and environmental perception E Pedersen and M Johansson

Cover project

Steely glaze Carpenter Lowings has created a giant light-reflective artwork for WilkinsonEyre’s latest office development Integrated into the narrow light well, the 40m-high artwork, comprising an asymmetric, stainless steel sculpture and dichroic glass, runs the full 10-storey height of London’s 8 Finsbury Circus. It was developed in response to a brief for both a focal point and a device to introduce reflected light into the depth of the building. ‘Folded Light is intended to provide a visual connection between people on every floor in the building with the presence and changing character of natural daylight,’ says Luke Lowings, co-owner of its creator, Carpenter Lowings Architecture and Design. The mostly triangular, three-dimensional folded panels of pattern-rolled stainless steel are varying sizes and folding angles, creating a single, continuous surface. The slender void space in which it sits measures 9m x 4.5m. The void is open at roof level, allowing the folds of the artwork to catch the almost vertical angle of light from the sky and create contrast with shadow below. The dimpled surfaces of the steel alternately face upward and downward in order to ‘exaggerate the contrast of light and shade, and bring the directionality, mutability, and colour of daylight into the building’.

The structure is made of 217 sheets of individually lasercut, drilled, bent and riveted stainless steel, just 1.2mm thick, mounted on welded aluminium frames to create a total of 47 three-dimensional forms. There are 90 steel folds included in the design so that its ‘unfolded length’ is just 2m longer than its height, at 42m. A 470kg, 36.5m-long vertical blade of dichroic glass separates the two sides of the artwork. This splits the spectrum into two complementary sections of contrasting colours when viewed from either side of the void. EQ2 Light was responsible for the overall lighting scheme for the development. When natural light levels are low, they can be supplemented by cool white light sources from above, while colours from below increase the drama of the artwork. Side-lighting at each floor level picks out the colour in the dichroic-coated glass. ‘It cannot be viewed as a complete installation from any single vantage point,’ says Lowings. ‘Its different sections are designed to relate individually to each floor, while remaining recognisable parts of the whole.’

Photography: Timothy Soar

‘It exaggerates the contrast of light and shade, and brings the directionality, mutability, and colour of daylight into the building’

Artwork: Carpenter Lowings Architecture and Design Lighting design: EQ2 LIght Architect: WilkinsonEyre




2017 18 March Junior Ready Steady Light Venue: Rose Bruford College Sidcup, Kent 21 March Ready Steady Light Venue: Rose Bruford College Sidcup, Kent 27-31 March Exterior Lighting Diploma Module 2 (Organised by the ILP) Venue: Draycote Hotel, Rugby 30 March Masterclass: Lighting Knowledge Series Human Responses to Light Venue: M-Shed, Bristol 4-9 April Euroluce Venue: Fiera Milano, Milan 27 April Masterclass: Lighting Knowledge Series Human Responses to Light Venue: The Lighthouse, Glasgow 27 April How to be Brilliant: at lighting for sculpture (Organised by the ILP) Speaker: Peter Pritchard, Pritchard Themis Venue: Marshalls Design Space London EC1 4 May Lighting Design Awards Venue: London Hilton Park Lane 9-11 May Lightfair International Trade Show and Conference Venue: Pennsylvania Convention Center 10 May Fundamental Lighting Course (Organised by the ILP) Venue: Regent House,Rugby 18 May Masterclass: Lighting Knowledge Series Human Responses to Light Venue: St-Martin-in-the-Fields, Trafalgar Square, London WC2

21 March: Ready Steady Light, Rose Bruford College

23 May Electric Know-How for Architectural Lighting Designers (Organised by the ILP) Venue: BDP, Clerkenwell, London EC1

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

25 May SLL AGM and Awards Venue: TBC 25 May How to be Brilliant (Organised by the ILP) Venue: Marshalls Design Space London EC1 9-12 June Guangzhou International Lighting Exhibition Venue: China Import and Export Fair Complex, Guangzhou 14-15 June Professional Lighting Summit (Organised by the ILP) Venue: Crowne Plaza, Glasgow 1-4 November Professional Lighting Design Convention Venue: Palais des Congrès de Paris 15-16 November LuxLive 2017 Venue: London ExCeL 16 November Lux Awards 2017 Venue: InterContinental London – The O2

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 march 2017