Light Lines January/February 24

The Society of Light and Lighting

VOLUME 17 ISSUE 1 JANUARY/FEBRUARY 2024

YES MINSTER

Schools light up a Leeds landmark

APPLIED SCIENCE

Translating circadian research to the real world

Editorial

January/ February 2024

FROM THE EDITOR SECRETARY Brendan Keely FSLL bkeely@cibse.org EDITOR Jill Entwistle jillentwistle@yahoo.com COMMUNICATIONS COMMITTEE: Andrew Bissell FSLL James Buck Iain Carlile FSLL Jill Entwistle Fiona Fanning Debbie-Sue Farrell Chris Fordham MSLL Rebecca Hodge Stewart Langdown FSLL Luke Locke-Wheaton Rory Marples MSLL Linda Salamoun MSLL 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 LL2 2024 IS 15 JANUARY PUBLISHED BY The Society of Light and Lighting 222 Balham High Road London SW12 9BS www.sll.org.uk ISSN 2632-2838 © 2024 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 Designed and printed in the UK George Eason Design www.georgeeason.design E: hello@georgeeason.design

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The discovery of the third photoreceptor in the eye followed years of research along diverse paths and a hypothesis that had its beginnings at least back in the 1920s. In some respects it was the end of a particular road, but as discovery often does, it gave rise to a lot more questions. It was the dawning of an understanding of just how mysterious the human circadian system is.

If our non-visual system is most sensitive to blue light, are we erroneously overlooking red light at the other end of the spectrum? Do rods and cones, an understood part of the visual system, still also play a role in the nonvisual system? Is there a universal formula for melanopic light given that research evidence so far reveals that we have very individual circadian sensitivities to light. And so on.

The big questions are how do we apply our knowledge to everyday lighting design, and is it premature to do so at this point?

It is an area addressed by Prof Manuel

Spitschan (Eye to the Future, p7). He identifies gaps in our knowledge and addresses the issue of translating what is gleaned in the lab to the everyday environment. 'While most laboratory studies have deployed relatively simple stimuli... the scenes we are exposed to in real life are typically more complex,' he says.

'From a neuroscience perspective, we have a learned a lot about the non-visual effects of light over the past decades,' he continues. 'Yet, more needs to be done to understand the underlying mechanisms, and understand their reach and limits in influencing us in real life.'

JILL ENTWISTLE JILLENTWISTLE @YAHOO.COM

CURRENT SLL LIGHTING GUIDES SLL Lighting Guide 0: Introduction to Light and Lighting (2017) SLL Lighting Guide 1: The Industrial Environment (2018) SLL Lighting Guide 2: Lighting for Healthcare Premises (2019) SLL Lighting Guide 4: Sports Lighting (2023) SLL Lighting Guide 5: Lighting for Education (2011) SLL Lighting Guide 6: The Exterior Environment (2016) SLL Lighting Guide 7: Office Lighting (2023) SLL Lighting Guide 8: Lighting for Museums and Galleries (2021) SLL Lighting Guide 9: Lighting for Communal Residential Buildings (2022) 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 (2022) SLL Lighting Guide 13: Places of Worship (2018) SLL Lighting Guide 14: Control of Electric Lighting (2023) SLL Lighting Guide 15: Transport Buildings (2017) SLL Lighting Guide 16: Lighting for Stairs (2017) SLL Lighting Guide 17: Lighting for Retail Premises (2018) SLL Lighting Guide 18: Lighting for Licensed Premises (2018) SLL Lighting Guide 19: Lighting for Extreme Conditions (2019) SLL Lighting Guide 20: Lighting and Facilities Management (2020) SLL Lighting Guide 21: Protecting the Night-time Environment (2021) SLL Lighting Guide 22: Lighting for Control Rooms (2022) Guide to Limiting Obtrusive Light (2012) Code for Lighting (2022) Commissioning Code L (2018) SLL Lighting Handbook (2018) CIBSE TM66: Creating a Circular Economy in the Lighting Industry (2021) CIBSE TM65.2: Embodied Carbon in Building Services – Lighting (2023)

sll.org.uk

January/ February 2024

Secretary’s column/Contents

Contents

A Happy New Year to everyone. I hope that you all had a great break and are raring to make a positive difference with light and lighting in 2024.

Following on from our brief coverage of Light Night Leeds in the last issue, David Battersby has written a more extensive article on the SLL's role in the event (see p5) which took place in October.

I'd like to take this opportunity to thank all of the volunteers and suppliers who were involved in the project, their time, effort and generosity were greatly appreciated: Volunteers: Amaar Farooq, Harry Forster and Jake Hardcastle of Thornley and Lumb; from Arup, Dan Lister, SLL president elect, Ana Davydchik, Ed Davenport, Elizabeth Cooper, Jessie Hayden and Helen Wright; Alex Draper, Hacel; Dominic McAndrew, Martech UK; Fiona Fanning, SLL; Helen Loomes, SLL president; Mark Kemp, Kemps Architectural Lighting; Rob Marsh, We‐ef Lighting; Simon Fisher, F Mark; Stephen Marley, Helvar; Steve Ripley, Systra – and, of course, David Battersby of Gamma Illumination.

Lighting equipment suppliers: Martin Architectural, iGuzzini, Light Projects, StudioTech, We‐ef, Lite, MaxiLED Lighting and Tryka.

Services and time: Gamma Illumination, F Mark, Arup, Kemps Architectural Lighting and Sigma Retail Solutions.

It was great to exhibit at LiGHT 23 at the Building Design Centre in November and see so many familiar faces, and some not so familiar. For the first time we also hosted the SLL Young Lighter 23 final there.

Well done to all those who entered, and especially the four finalists.

The winner of the competition, Teresa Carrasco (see p4), was presented with her winning trophy and gave her paper once more at the SLL’s Light2Perform at ExCeL in early December. Teresa receives the SLL Young Lighter Trophy and £1000 of prize money, while all finalists will receive £250 for reaching the final. It was a pleasure seeing and talking with the members. This was the first year of Light2Perform and we are keen to expand the exhibition and

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For more details of Light+Intelligent Building Middle East: https://light-middle-east. ae.messefrankfurt.com/ dubai/en.html For PQP SKILLcard application process: www. cibse.org/get-involved/ societies/society-of-lightand-lighting-sll/sllmembership/pqp-ecs-skillcard

develop the lighting conference programme for Light2Perform 24.

We are looking forward to exhibiting at Light+Intelligent Building Middle East, from 16-18 January, at the Dubai World Trade Centre, and hope to see many CIBSE and SLL members from the UAE region and beyond. It has been a few years since we have attended the exhibition and conference, during which time the show has grown in size, increasing the number of both exhibitors and visitors.

On administrative matters, the SLL and CIBSE subscription renewal notices have been delivered to all members and if you have any questions regarding renewing your membership for 2024 please don't hesitate to let me know.

Remember that with SLL membership you can apply for the ECS Professionally Qualified Person card (PQP SKILLcard) to gain access to the construction sites you are working on (see box for details regarding the card application process).

SLL nominations and the date of the 2024 Annual General Meeting will be sent to all members soon. At the moment, the AGM is scheduled to take place on Tuesday 14 May in Leeds.

BRENDAN KEELY BKEELY @CIBSE.ORG

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EDITORIAL

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SECRETARY'S COLUMN

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NEWS

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CLASS ACT

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EYE TO THE FUTURE

David Battersby on the latest Pockets of Light event: from engaging school students with light to illuminating a city landmark

How can non-visual and circadian neuroscience be translated to the real world? Prof Manuel Spitschan identifies gaps and opportunities

10 ILLUMINATING READ

In this edited extract from his new book Stories with Light, co-written with Francis Pearce, lighting designer Michael Grubb explores the science, history, magic and meaning of light

13 GLOWING COLOURS

The SLL's 2023 Ready Steady Light: creativity against the clock

CAUGHT IN THE

14 HEADLIGHTS

Iain Carlile focuses on a recent LR&T paper which looks at the importance of CCT for vehicle lights

OF THOUGHT 15 TRAIN Top 5: Bob Bohannon's best railway stations

16 EVENTS

COVER: Leeds Minster lit by SLL members from designs by local schoolchildren as part of Light Night Leeds

Gamma Illumination

FROM THE SECRETARY

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News

January/ February 2024

THE LATEST NEWS AND STORIES

News CIRCADIAN LIGHT IS WINNING TOPIC FOR YOUNG LIGHTER

María Teresa Aguilar Carrasco (left) was the winner of SLL Young Lighter 2023 with her presentation on CircaLight, a new circadian light assessment tool for the Grasshopper environment.

Carrasco is an architect, who graduated from the University of Seville in 2019. She is now a researcher at the Department of Architectural Construction at the Higher Technical School of Architecture of Seville, and studying for a PhD in architecture. Her doctoral research encompasses lighting and energy efficiency, and focuses on the impact of lighting, natural and electric, on visual comfort and the health of individuals.

The final of Young Lighter, now in its 29th year, was held at LiGHT 23 in November, hosted by SLL president elect Dan Lister. There were three other finalists taking part. Anna Freiesleben (second left) of Michael Grubb Studio looked at Light Beyond Earth: Illuminating life on exoplanets, while Irene Mazzei (centre), Edinburgh Napier University/Stoane Lighting Knowledge Transfer Partnership) examined improving sustainability in the lighting industry. The fourth finalist, Tom Ruddle (right) of EGG Lighting, also chose a similar theme with his paper, Lighting Remanufacture.

The Young Lighter competition was going from strength to strength, said Lister. 'It provides a unique platform for those in the early years of their lighting careers. Their presentations allow the young lighters to illustrate their knowledge and research on a lighting subject, hone their presentation skills, and raise their profile within the industry.'

The winner of the competition was announced on 5 December 2023 at Light2Perform, when Carrasco gave a second presentation of her winning paper.

ON THE LIGHTER SIDE… Encouraging that light pollution was one of the key factors, along with sustainability, that has (at least for the moment) put paid to the ambitions of MSG Entertainment to plonk its giant illuminated orb in Stratford, east London.

At 90m tall (as high as Big Ben) and 120m wide, and together with artificial lighting within the development, it would have 'significant adverse effects' for those living in nearby buildings, said the report produced by WSP for the Greater London Authority (GLA).

Assuming that it would have copied its recently opened counterpart in Las Vegas

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(above), which features LED screens displaying 360 degrees of video and adverts for up to 24 hours a day, that was probably something of an understatement.

MSG, run by Trump donor James Dolan, apparently attempted to alleviate residents’ concerns at one point by offering blackout blinds when they expressed fears about not being able to sleep.

CLIMATE PLAN UPDATE CIBSE has updated its Climate Action Plan in the fourth annual review after producing its first CAP in 2019. The 2023 updates include: • Mandatory CPD on sustainability and net zero from 1 January 2024 for all corporate members of CIBSE. • Continue to develop guidance and training offering on net zero carbon buildings.

• Continue active involvement with Net Zero Carbon Buildings Standard.

• Introducing draft ‘Mirror climate action plan’ for individuals and organisations in the CIBSE community, suggesting actions and commitments.

• Progressing office move to a new London location, with net zero and sustainability a key part of the brief.

CIBSE is inviting feedback on its draft Mirror Climate Action Plan, available to view in the CAP. Comments should be sent to: jgodefroy@cibse.org

FINAL SPEIRS AWARDS The joint winners of the 2022/23 Jonathan Speirs Scholarship Fund (JSSF) award are Edward Turner and Samuel Walker. They will be the final recipients as the awards draws to its planned close after 10 years.

Turner is studying for an MA in architecture at the Royal College of Art. Initially concerned with natural light his recent project, Batteries Not Included, reimagined the Blackpool Illuminations, with an inventive use of kinetic structures and kinetic architecture to generate and store electricity.

The scholarship will support Turner in starting his own spatial design practice.

Walker is studying architecture at Coventry University. He has a particular interest in light pollution, exploring how darkness, subtle lighting and contrast can shape space and experience.

The scholarship will support him in working with professionals to set up an educational platform for those interested in lighting design and sustainability.

sll.org.uk

January/ February 2024

Events

CLASS ACT

David Battersby on the latest Pockets of Light event, that began in engaging school students with light and culminated in illuminating a city landmark

ack in January 2023, a core team was formed from the SLL's members, comprising myself, Dan Lister, Simon Fisher and Elizabeth Cooper. This team was charged with creating a Pockets Of Light event at Light Night Leeds in the memory of Leeds-based lighting designer and SLL past president Liz Peck, who helped to originate and organise the PoL events.

The concept of Pockets of Light, previously held in York in 2016 and Oxford in 2017, was based on the idea of working with pupils from selected schools to design temporary lighting schemes for buildings as part of a larger lighting event, previously the SLL's Night of Heritage Light at Illuminating York and Oxford's Curiosity Carnival. These schemes are then realised using the skills and equipment of SLL members.

We met with the Light Night Leeds team in early 2023 to explore the idea of working with them. They were really excited about the idea, and the whole concept of Pockets of Light, especially given the history of the

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project and why we particularly wanted to have this in Leeds.

While discussing potential heritage buildings around Leeds city centre, the Light Night team mentioned Leeds Minster was interested in being part of the overall festival. This was an excellent building for us not only because of its heritage but also its very prominent position on the Leeds skyline. When the idea was suggested to them by the Light Night team, the people responsible for the minster were delighted at the prospect of their facades becoming part of the event.

Working with the Light Night team, two schools were chosen for the Pockets of Light presentation and workshop, one primary (Alder Tree Primary) and one Secondary (Leeds West Academy).

The basis of

the presentation and workshop was taken from the original PoL events and covered what we do as lighting designers and the areas in which we work. The idea of the presentation was to get the students to think about light and lighting, how light can affect your mood and how it can be used to emphasise points of visual interest. The workshop covered the basics of how to light a facade, spotlighting, floodlighting and how a light source's distance from a surface can affect its visual texture. It also covered basic additive and subtractive colour mixing.

The school presentations were given in July 2023 by myself, Dan Lister, Anastacia Davydchik and Jake Hardcastle with the design submissions completed during the visit.

The primary school presentation was given to a total of 60 year-nine students. While the students worked on their designs, the team noticed a drawing of a frog. When the student was asked ‘Why a frog?’ The response was ‘because I like frogs’, something we couldn’t really argue with. The team worked through this idea with the student to develop it into the Protect the Planet projection used on each side of the main tower. We asked the student to submit a drawing of the frog which we used as the design of the gobo for the event.

The presentation at the secondary school was to a more focused group of 15 mixed-age students chosen by the music and drama department. It was a bit surprising that, while the students were working on their designs,

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Events

yet another drawing of a frog was spotted.

The team narrowed down the submissions to a shortlist for each area of the minster, ensuring we could deliver any of the designs and that the combination of any designs would work in conjunction with each other. The final winning submissions were decided in collaboration with both the minster and the Light Night Leeds team. Both were really impressed with the ideas and creativity of the students, one of the comments being, ‘the more frogs, the better’.

The designs were worked up by the team, making sure that the whole building was cohesive and winning entries harmonised with each other. The ideal kit list was established and, with the kindness of our industry, we managed to borrow all the equipment needed.

This included 12 gobo projectors, seven beam shapers, 60m of festoon and 45 RGB fittings with a mix of beam angles, powers and style (linear and spotlight). All the RGB fittings were controlled by DMX, with four separate

January/ February 2024

systems used due to on-site cable restrictions.

All the controls were preprogrammed so only tweaks would be needed during installation.

SLL president Helen Loomes joined us to work through the final details of the visit of Liz Peck's family on the Thursday evening. The event went without a hitch, with Liz’s family impressed with what we had brought to Light Night Leeds in her memory. It was great to see other familiar faces from the society coming to see the minster too.

The team managed to catch up with some of the teaching staff from the secondary school and they were really impressed with the scale of the installation. ‘We knew you’d do it but had no idea how,' said one of them.

After the event, artists' lanyards and the interpretation boards used during the event were delivered to the schools to be given to the students of the winning entries. I believe this will give them a lifelong memory and hopefully they will think more about light and the lit environment around them.

It was a very long few days on-site for the team and volunteers but it was a pleasure to work on and be a part of this event. The end result was excellent and there have been many comments about how much the final installation looked like the students' concept designs, something which the team is extremely proud of. A big thank you goes to all the suppliers and volunteers who gave their time, support and resources to this project.

The frogs continue to make me chuckle and I think Liz would have appreciated them too...

David Battersby, MSLL, is senior lighting designer at Gamma Lighting, and SLL representative and CIBSE committee member for the Yorkshire region The Light Night Leeds event took place in mid-October 2023

Winning entries Protect the Planet: Rihana, Alder Tree Primary Academy ‘I love frogs and nobody respects frogs and we should protect the planet’ Music Builds Community: Lizzie, Leeds West Academy The basis of this submission was the church's relationship with music and how music builds relationships, community and friendship We Are All Diverse: Acacia, Tegan, Paris and Layla, Alder Tree Academy The theme of diversity was picked up by all the above students, using bold colours and patterns, various aspects were taken from each design

All images Gamma Illumination

Religion is Pure: Hayden, Leeds West Academy ‘A tree represents strength, individuality and expression, also representing growth and interconnection of everything and everybody’

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Sema, Alder Tree Primary Academy The lighting design uses bold colours and strong contrast to celebrate the architectural details and forms of the minster facade

sll.org.uk

January/ February 2024

Research

EYE TO THE FUTURE How can non-visual and circadian neuroscience be translated to the real world? Prof Manuel Spitschan identifies gaps and opportunities ight profoundly influences our physiology, behaviour, health and wellbeing. Kicked off by the discovery of the intrinsically photosensitive retinal ganglion cells expressing melanopsin in the early 2000s, the way we think about lighting in the built environment has been revolutionised. As we have gathered evidence from laboratory studies, the translatability of findings and their significance for practice is often not very clear. From the perspective of neuroscience, what is missing to make the scientific knowledge count?

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OF MICE AND MEN: NON-VISUAL NEUROBIOLOGY The history of melanopsin starts not with its discovery in 1998¹ but three-quarters of a century earlier. As a graduate student at Harvard, Clyde Keeler observed an anomaly in a strain of blind mice he was examining in the laboratory². When shining light on their eyes, their pupils would constrict to the light stimulation. Writing in 1927, Keeler hypothesised even then that the iris is directly light-sensitive.

Almost 35 years later, Bouma published an article in Nature describing the sensitivity of the human pupil to light of different wavelengths³. By illuminating the eye with varying light spectra at different intensities, Bouma observed which wavelengths of light were most potent in reducing pupil size. By comparing it with contemporary knowledge about the sensitivity of the rods and cones, he determined that neither the cones nor the rods – the photoreceptors that help us see – were underlying the pupil’s response to light. Now we know that the size of the pupil – as well as the suppression of melatonin by light and the synchronisation of our clock by the light-dark cycle – is due to melanopsin⁴,

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a light-sensitive protein found in a set of nerve cells in the retina.

Foreshadowing the discovery of melanopsin another 35 years later, Bouma wrote: 'The functional significance of outcome of experiments is still uncertain. It may turn out to be related to other adaptive processes in the human eye.'

In 2023, these 'other adaptive processes' have turned out to be quite far reaching in human physiological function and are still under active investigation in scientific studies.

Some of these simply describe how light affects the clock, hormones and thinking, and some studies try to understand the underlying mechanisms. The latter type of study is very challenging in humans, and therefore, most – but not all – of what we know about the mechanisms underlying the non-visual effects of light comes from animal studies.

STANDARDS FOR LIGHT AND LIGHTING Realising the immense real-world significance of melanopsin for practical lighting, a group of researchers came together in Manchester in 2013 to discuss how to make the emerging knowledge count in the real world. In 2014, Lucas and colleagues published their landmark paper 'Measuring light in the melanopsin age', and following this, the International Commission on Illumination (CIE) developed a

series of standard spectral sensitivity curves and quantities creating the necessary metrology to describe a non-visual stimulus.

The melanopic equivalent daylight illuminance of a light, abbreviated as melanopic EDI, is now the most commonly used metric, reflecting the illuminance of standard daylight (D65) that has the same effect on the melanopsin system as the light source under examination. This system – the CIE S026 system⁶ – is now the standard for quantifying the non-visual effects of light, and evaluating lighting and lighting solutions in terms of the effect on circadian and neuroendocrine physiology, cognition and behaviour. The application of this new metrology is aided by training and tutorials, as well as openly accessible software tools such as our luox web platform⁷ (see Light Lines May/June 2021).

In 2019, a second workshop took place in Manchester with the goal of deriving consensus recommendations for optimal light exposure at varying times of the day. These recommendations, which were published by Brown and colleagues in 2022⁸, suggest >250 lux melanopic EDI during daytime waking hours, <10 lux melanopic EDI in the pre-sleep environment and <1 lux melanopic EDI during sleep.

Based on a review of primarily laboratory studies, and supported by converging evidence from field studies, the recommendations are a landmark, and hopefully will be translated into policy and regulations in the future. Melanopic metrology has already found its way into national specification schemes relevant for lighting design in some countries.

GAPS IN OUR KNOWLEDGE

'The impact of light varies depending on who is exposed to it. The notion of a 'circadian standard observer' is called into question'

While we understand some aspects of the non-visual effects of light, we still lack a deeper understanding of others. We recently identified knowledge gaps⁹ that must be closed through principled and systematic investigation (see Figure 1).

While the primary role of melanopsin in driving these responses has been established through converging evidence, it remains less clear how the

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Research

cones and the rods possibly contribute to nonvisual function.

While most laboratory studies have deployed relatively simple stimuli by using either homogeneous stimulation shown through a specialised piece of equipment or room illumination, the scenes we are exposed to in real life are typically more complex. As light can vary across a range of parameters – in terms of intensity, spectrum, temporal pattern, and spatial distribution¹⁰,¹¹ – the melanopsin system may (or may not) encode these parameters and carry these signals further.

Recent research has identified marked individual differences in how we respond to light¹². In a lab study investigating melatonin suppression under evening illumination, the most sensitive individual was more than 50 times more sensitive than the least sensitive individual¹³. In biology, this is a considerable phenotypical variation. This has a practical and significant consequence for specifying lighting for people, as the impact of light varies depending on who is exposed to it. The notion of a 'circadian standard observer' is called into question by these stark differences.

Beyond differences in sensitivity, people will also be exposed to different types of light in their daily lives. Akin to 'sleep deserts' – neighbourhoods where social and environmental factors lead to sleep health inequity¹⁴ – public and home lighting is similarly stratified.

We must find ways to deliver good light at the right time – not just to those privileged to have good daylight access and highquality home lighting – but to everyone.

But light is only one aspect that controls our circadian clock and sleep-wake behaviour.

From laboratory and field studies, we know that what and when we eat, our exercise and

'Beyond differences in sensitivity, people will also be exposed to different types of light in their daily lives'

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January/ February 2024

Integration of rod-cone signals with ipRGCs and novel photoreceptor-based metrology Integration of light with other signals in circadian, neuroendocrine and sleep physiology Individual differences in light exposure and light equity Individual differences in light sensitivity Mapping the parametric space of light to physiological responses

� Fig 1: recently identified knowledge that must be closed through principled and systematic investigation, according to Spitschan – 'While we understand some aspects of the non-visual effects of light, we still lack a deeper understanding of others'

6 Develop evidence-based standards in lighting marketing for non-professionals 4 Defining actionable 2

light exposure limits

Cumulative data gathering

and recommendations

and sharing, allowing the development of accurate models that aid implementation

� Figure 2 3

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Moving away from

Recognising healthy light

Weird samples to

exposure as a human right

incorporate diversity

with expected benefits to community health

1 Address knowledge gaps through adversarial collaborations and international consortia

� Fig 2: Spitschan's proposed series of individual steps 'that will advance our knowledge and move us to deliver an evidence-based and systematic approach to lighting firmly grounded in science'

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January/ February 2024

activity patterns and even social and psychological factors can influence our physiology fundamentally.

In the laboratory, we can isolate these factors but cannot in real life. Consequently, we do not know to what extent these different influences contribute to our circadian entrainment and trade-off on each other.

'We believe that healthy light exposure is a fundamental human right that should be recognised as such'

A ROADMAP What needs to be done to fill these knowledge gaps? We recently proposed a series of individual steps (see Figure 2) that will

Research

advance our knowledge and move us to deliver an evidence-based and systematic approach to lighting firmly grounded in science⁹.

No laboratory or research group can 'solve' the knowledge outlined above independently.

Instead, a more collaborative approach is needed; the parametric space of light – variations across intensity, spectrum, temporal pattern and spatial distribution – could be tessellated and investigated through harmonised data collection and reporting protocols.

One approach that could arbitrate between different approaches and models would be an adversarial collaboration, in which researchers with different viewpoints or working models work together to answer a research question¹⁵. Data collected in different laboratories could be entered into a data pool, so our knowledge and evidence base can grow with time, and our insights can be updated.

A global collaborative approach would also enable the recruitment of more diverse participant samples and help us generate

References • 1 Provencio, I, et al, Melanopsin: An opsin in melanophores, brain, and eye.

Proc Natl Acad Sci U S A, 1998. 95(1): p340-5 • 2 Keeler, CE, Iris Movements in Blind Mice. American Journal of PhysiologyLegacy Content, 1927. 81(1): p107-112 • 3 Bouma, H, Size of the static pupil as a function of wavelength and luminosity of the light incident on the human eye. Nature, 1962. 193: p690-1 • 4 Spitschan, M, Photoreceptor inputs to pupil control. J Vis, 2019. 19(9): p5.

• 5 Lucas, RJ, et al., Measuring and using light in the melanopsin age. Trends Neurosci, 2014. 37(1): p1-9 • 6 CIE, CIE S 026/E:2018: CIE System for Metrology of Optical Radiation for ipRGC-Influenced Responses to Light. 2018, CIE Central Bureau: Vienna.

• 7 Spitschan, M, et al, luox: validated reference open-access and open-source web platform for calculating and sharing physiologically relevant quantities for light and lighting. Wellcome Open Res, 2021. 6: p69 • 8 Brown, TM, et al, Recommendations for daytime, evening, and night-time indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults. PLoS Biol, 2022. 20(3): pe3001571 • 9 Spitschan, M and DS Joyce, Human-Centric Lighting Research and Policy in the Melanopsin Age. Policy Insights from the Behavioral and Brain Sciences, 2023. 10(2): p237-246 • 10 Spitschan, M, Time-Varying Light Exposure in Chronobiology and Sleep Research Experiments. Front Neurol, 2021. 12: p654158 • 11 Webler, FS, et al, What is the 'spectral diet' of humans? Curr Opin Behav Sci, 2019. 30: p80-86 • 12 Spitschan, M and N Santhi, Individual differences and diversity in human physiological responses to light. EBioMedicine, 2022. 75: p103640.

• 13 Phillips, AJK, et al, High sensitivity and interindividual variability in the response of the human circadian system to evening light. Proc Natl Acad Sci USA, 2019. 116(24): p12019-12024 • 14 Attarian, H, et al, Addressing sleep deserts: A proposed call for action. Sleep Health, 2023 • 15 Rakow, T, Adversarial collaboration, in Avoiding Questionable Research Practices in Applied Psychology, W O'Donohue, A Masuda, and S Lilienfeld, Editors. 2022, Avoiding Questionable Research Practices in Applied Psychology: Cham

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evidence beyond studies performed preeminently in Weird (Western, educated, industrialised, rich, democratic) contexts.

The recent recommendations by Brown and colleagues represent an excellent first step in prescribing good light exposure across the day.

How exactly these can be turned into policies, specifications and policies is an open question.

Importantly, we believe that choice and behaviour are key factors in bringing the right light to people at the right time, and we are currently taking first steps in understanding how we can support behaviour change when it comes to light. We believe that healthy light exposure is a fundamental human right that should be recognised as such.

Awareness is critical, and important multipliers of the neurobiology of non-visual neurobiology are architects and lighting designers. Finally, it is key to empower nonprofessionals to make good decisions about light, which could be realised through public health awareness campaigns as well as product packaging containing information about the melanopic properties of light – not just luminosity, correlated colour temperature and colour rendering.

CONCLUSION AND OUTLOOK From a neuroscience perspective, we have learned a lot about the non-visual effects of light over the past decades. Yet, more needs to be done to understand the underlying mechanisms, and understand their reach and limits in influencing us in real life. A key step is the identification of 'known unknowns'. The journey may be long, but we are on the right path for bringing healthy light in an evidencebased fashion.

Manuel Spitschan, recipient of the 2020 Jean Heap Research Bursary from the SLL, is professor of chronobiology and health at the Technical University of Munich, and research group leader at the Max Planck Institute for Biological Cybernetics Further reading • Spitschan, M, & Joyce, DS (2023). Human-centric lighting research and policy in the melanopsin age. Policy Insights from the Behavioral and Brain Sciences 10(2), 237-246. https:/ /doi.org/ 10.1177/23727322231196896

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Books

January/ February 2024

Jane Davies

ILLUMINATING READ

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sll.org.uk

January/ February 2024

Books

In this edited extract from his new book Stories with Light, co-written with Francis Pearce, lighting designer Michael Grubb explores the science, history, magic and meaning of light have written a rather big book – more is the pity... and I am now just beginning to go over the [manuscript] for the second time, which is a horrid bore,’ Charles Darwin once confided in a letter. Even without having authored the Origin of Species, Darwin would probably have won his place in biology with his last work, The Power of Movement in Plants, though. However irksome, his investigation of phototropism stimulated an entire field of research known as photobiology, which also includes photosynthesis, photomorphogenesis (light-driven plant growth), bioluminescence and non-visual photo-reception.

Until recently, the importance of darkness in these processes was largely overlooked. It wasn’t until this century that the term scotobiology was invented as an acknowledgement that darkness affects a wide range of natural occurrences from flowering, dormancy and senescence in plants, to diapause in insects and on to the workings of our own body clocks. But the clues had been there even before Darwin put pen to paper.

The touch-me-not plant (Mimosa pudica) will fold its leaves when rain falls on them but left to their own devices, they open or close just once a day. In the early 18th century Jean-Jacques d’Ortous de Mairan showed that they would follow this daily cycle with or without the stimulus of light – by keeping touch-me-nots in a dark closet.

He concluded that plants could somehow sense the sun without seeing it, but what he’d actually found was a pattern set by an inbuilt regulator tied – approximately – with the lightdark daily cycle. Its job is to help anticipate changes in the environment.

In humans, the release of cortisol and melatonin, which help to regulate blood sugar, follows just such a circadian pattern. The two hormones have opposing rhythms: about three hours before we wake, our cortisol levels begin to rise so that we are ready to be active, and

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Jane Davies

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In the John Hayes screenplay for the classic Alfred Hitchcock movie of 1954, Rear Window, news photographer ‘Jeff’ Jeffries’s broken leg has trapped him in ‘a world shrunk down to the size of a window'. It looks out on those of the block behind, each a small stage, on which a story unfolds; one plays out as a murder. When the killer comes for him, Jeff looks for a weapon ‘and almost by instinct, he snatches up his flash holder and the small packet of bulbs', loading and firing – momentarily blinding the murderous Thorwald with a million lumens at each explosion. Thorwald sees only ‘big twisting balls of blinding yellow… He stumbles backward again, trying to brush the light away from his face, almost as if it were a solid, enveloping substance.’

James Thurber wrote metaphorically that, ‘there are two kinds of light: the glow that illuminates, and the glare that obscures'. More literally, apart from the excruciating afterimage from the flash bulb, Thorwald’s pupils would have taken up to 15 seconds to return to normal after each assault.

Our pupils constrict in bright light and dilate in the dark. You might think that these reflexes are simply the reverse of one another but they work in different ways, at a different pace and on different parts of the brain.

Although they both involve more than one type of nerve cell: a sensory neuron, a motor neuron and a third type that acts as a relay between them, the signal from pupil to brain and from brain to body – muscles and glands – follows a different path when the lights go on and when they go off.

In bright light, information goes to the mid-brain and on to a region called the oculomotor complex, which tells the iris muscles to tighten. The dark reflex involves sending a signal to the hypothalamus, the reply travelling via the spinal cord. Pupil dilation isn’t just triggered by sudden low light, it can also be set off by a loud noise or pinching the neck, bracketing our response to the dark with other senses. Although he had little science to base it on, the 18th-century philosopher Edmund Burke may have been right when he said that darkness is ‘known by experience to have a greater effect on the passions than light'.

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Books

melatonin, which plays a part in getting us to sleep, is suppressed.

How this happens was a mystery until 2002 and the discovery of a third type of photoreceptor in the eye which doesn’t enable us to see but which helps set a master clock in the brain. Non-visual photo-reception keeps our wake/sleep cycle in step and stops other vital activities from drifting.

‘You can be visually blind, you can have absolutely no image detection whatsoever, and yet you can still regulate your body clock,’ said Professor Russell Foster.

The neurons that Foster and his team at Oxford University helped discover express a photopigment called melanopsin, which reacts to roughly the same wavelengths of light as the opsins that we mammals ‘lost’ in our early evolution.

‘Rods and cones of the retina provide us with our sense of space or vision, but a small number of photosensitive retinal ganglion cells detect the overall amount of light in the environment and then align the body clock – providing us with our sense of time,’ Foster explained.

Our body clocks are ‘entrained,’ continually being reset by the daily cycle of dark and light but they can’t just be left to tick over, switching hormones on and off on a pre-set timer, because there are seasons with changing day-lengths to cope with and, in any case, nights are shorter than days on average.

Because sunlight is refracted by the atmosphere, it can still reach the ground while the sun is below the horizon; even at the equinox at the Equator, daytime lasts about 14 minutes longer than night.

The higher the latitude and the nearer the solstice, the more pronounced the effect and the greater the need for an internal regulator independent of the light/dark cycle.

An old report in the Chinese Recorder, a newspaper for Presbyterian missionaries, describes how in the realm of K’o-fu-ch-a, the days in summer are so long and the nights so short that ‘in

'Even at the equinox at the Equator, daytime lasts about 14 minutes longer than night'

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January/ February 2024

little more than the time necessary to cook a mutton chop, the sun rises again'.

At the poles, where the sun only rises or sets once a year, because the Earth’s axis tilts away from it, the summer sun appears to spiral higher into the sky until, for a week or so either side of the solstice, it seems to stand still, then winds its way down again and out of view. When the ninthcentury Irish monk Dicuil described the period of midnight sun in Thule, the mysterious Far North of the Ancient Greeks and Romans, he wrote that even when the sun dipped behind a hill, ‘a man could do whatever he wished as though the sun were there, even remove lice from his shirt.’

Solstice comes from the Latin 'sol' for sun and 'stare', to stand still. As Clarence Darrow pointed out in the 1925 Scopes Monkey Trial, if the sun were literally to halt in the sky, the Earth would be ‘converted into a molten mass of matter.’

Fortunately, the world keeps spinning and at 69 degrees north at Igloolik, in Nunavut, Canada, within the Arctic Circle, the sun is below the horizon for 46 days a year but above it for 66 days. Twilight extends from mid-April and into late August.

For all that, though, no words could express ‘the

utter weariness of the soul that must inevitably attend the vigils of those long Arctic nights,’ according to lieutenant Adolphus Greely, a survivor of the Lady Franklin Bay Expedition which began in 1881 but was stranded for four years about 400 kilometres from Igloolik.

Taking the scientific readings they were tasked to do in the fierce cold and the low light must have been hell. Even in winter, while the expedition’s astronomer struggled to work by candlelight, a team including the doctor and two Inughuit members of the party hunted. Yet, ‘a mere knowledge that the date had arrived on which the sun was to begin its return to them was sufficient even in the still impenetrable darkness to revive the spirits and even improve the health of the men,’ Greely wrote.

Michael Grubb is the principal of Michael Grubb Studio and a member of the SLL Council Stories with Light will be available in early 2024.

See www.michaelgrubbstudio.com for more information

'The blue and the dim and the dark cloths Of night and light and the half-light' - WB Yeats, He Wishes for the Cloths of Heaven The world’s largest movement of creatures takes place under the moon.

Marine biologist Geir Johnsen of UIT, the Arctic University of Norway, has spent a decade researching off the Svalbard archipelago. Until recently it was thought that sea creatures there enter a general resting state when the sun goes down and the long polar night draws in. But his research shows that, ‘as the sun becomes less and less visible in the sky… the moon, the stars and even the aurora borealis become more and more important’ so that, under their influence, millions of krill make their way up from 60m below, in such huge number that they attract deep sea fish to feed. It has been called the ‘biggest daily migration on the planet'.

Some Arctic marine organisms such as algae respond to light levels as low as one millionth that of daylight. This discovery could be critical. Most creatures have a threshold for their responses to light. Algae have special proteins that provide a safety valve to stop their cells being damaged by too much light. But there is a limit to how much stress they can take.

Why does that matter? A shrinking icecap has brought increased sea freight, oil and gas extraction, fishing and tourism, and with them greater light pollution. As the summer ice gets thinner or melts altogether, more light penetrates the sea. This not only disrupts the ‘foodweb’ but, ‘about 50 per cent of the oxygen that we breathe is from these microscopic algae in the world’s oceans,’ Johnsen warns. ‘Without those key groups there would be no life.’ Or, as Robert Hunt put it in The Poetry of Science, ‘light is necessary to life; the world was a dead chaos before its creation, and mute disorder would again be the consequence of its annihilation.’

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January/ February 2024

Events

� Arup's winning scheme was based on the seasons, using different lighting techniques and colours to denote each scene

� The inspiration for Xavio Design's scheme was the Mexican Day of the Dead. The scheme scooped both Artistic Award and Peer Prize

GLOWING COLOURS With limited time and limited kit, the SLL's 2023 RSL as usual challenged the participating teams to conjure up winning lighting schemes n a well-supported competition, Arup won the Technical Award at the 2023 SLL Ready Steady Light with a design based on the four seasons, using different lighting techniques and colours to express each scene.

The team from Xavio Design pulled off a double, winning both the Artistic Award and the Peer Prize, judged by the contestants taking part. Their inspiration was the Día de los Muertos (Day of the Dead), with a playful and colourful scheme that reflected the vivid Mexican celebration.

Judges for the Technical Award were Andrew Bissell, lighting partner at Ridge and Partners and SLL immediate past president, alongside Juan Ferrari and Kael Gillam, project director and principle lighting designer respectively at Hoare Lea. The Artistic Award was judged by Emma Cogswell, projects manager IALD UK, and Beatrice Bertolini of Equation Lighting Design, also from the IALD. Joining them was Sofia Alexiadou, programme director for the BA Creative Lighting Control course at Rose Bruford, as well as programme director on the MA Light in Performance course.

'This year's participants showed great

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initiative,' said Emma Cogswell. 'Working within a tight time scale and small portfolio of lighting instruments, the teams really pulled off some engaging and endearing schemes’.

'The overall skills and understanding of lighting of the participants were commendable,' said Juan Ferrari. 'Arup's design balanced perfectly the understanding of producing a visual piece that was creative and engaging while also being sustainable.'

One of the SLL’s flagship events, the annual Ready Steady Light competition gives competing teams just three hours and a limited range of equipment to design and set up temporary exterior installations in the grounds of Rose Bruford College (RBC) in Sidcup, Kent.

The main aim is to give students an opportunity to gain some hands-on experience, experimenting with lighting techniques and working alongside practising lighting professionals. Each year, three teams from the UCL light and lighting MSc take part and, this year, a team from RBC. Students enrolled in the college's lighting and design BA and MA courses always support the event, which this year was organised by Daniel Paget, project lead

at RBC, together with Ryan Dunnet, project technical manager.

Ready Steady Light, held on 17 October 2023, was organised in association with Rose Bruford College in Sidcup, Kent, and the International Association of Lighting Designers (IALD)

TEAMS Arup Cundall Equation lighting Fosters+Partners Hilson Moran IALD Mid Ridge Rose Bruford College Stantec UCL x 3 WSP Xavio Design

SPONSORS Centre Stage Solutions Lumino Distribution Urbis Schréder

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LR&T essentials

January/ February 2024

CAUGHT IN THE HEADLIGHTS Iain Carlile focuses on a recently published paper in Lighting Research and Technology which looks at the importance of correlated colour temperature for vehicle lights ehri et al have examined the impact of different correlated colour temperatures of vehicular headlights on drivers. Both visual and non-visual effects were investigated during a simulated driving task in which 40 participants took part in three different sessions, each lasting 45 minutes.

Those taking part in the study were all people working as taxi drivers. This was to avoid results being influenced by inexperienced drivers or depreciation of visual acuity caused by age.

Only those with a minimum of five years' driving experience and maximum age of 50 years old were invited.

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'As CCT decreased, participants exhibited longer reaction times, a greater number of errors and reported increased sleepiness'

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Various inclusion criteria (for example, general health, mental health, eye conditions and so on) were used to select the final 40 participants. The median age was 33 years.

During the experimental sessions the participants undertook a simulated driving task, with each session using car headlights of differing correlated colour temperatures (CCT) – 3176K, 4358K and 6923K – all of them providing an illuminance of five lux perpendicular to the eyes of the participants.

During each session the participant’s heart rate variability (HRV), psychomotor vigilance task and Karolinska sleepiness scale were measured before and after the simulated driving task. Also, at the end of the trials achromatic far and near visual acuity tests, and achromatic far and near contrast sensitivity tests were undertaken.

The results of the study identified that CCT did not affect achromatic far and near visual acuity. However, it was noted that CCT did have an impact on achromatic near and far contrast sensitivity, with an improved achromatic contrast sensitivity from the higher CCT. As CCT decreased, participants exhibited longer reaction times, a greater number of errors

and reported increased sleepiness. With respect to HRV, the most significant physical changes were observed at lower CCT. The authors suggest that both the visual and non-visual performance of drivers was enhanced when high CCT values were used for automotive headlights.

Iain Carlile, FSLL, is a past president of the SLL and a senior associate at dpa lighting consultants

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 SLL website (www.sll.org.uk) Visual and non-visual responses of drivers to simulated LED headlights varying in correlated colour temperature A Mehri, R Golmohammadi, M Aliabadi, M Farhadian, JD Bullough and M Samavati

A reminder that Vol 55, Issue 7&8 of Lighting Research and Technology is a special issue designed to highlight the work of early career researchers in lighting (see Light Lines November/December 2023).

Guest edited by Eleonora Brembilla of Delft University of Technology and Kynthia Chamilothori of Eindhoven University of Technology, it is essentially research from PhD students. The 10 articles cover urban lighting, daylighting, nonimage-forming (NIF) effects of lighting, and eye safety when using virtual reality displays. https://journals.sagepub.com/ home/LRT

Diagram of driving conditions in the simulator room

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sll.org.uk

January/ February 2024

Top five

TRAIN OF THOUGHT ailway stations are surprisingly complex entities. Of course their basic purpose is to facilitate a journey by train, but to navigate the larger ones can be a journey in itself. They also represent time, not just the rigid time of the railway timetable, or the diurnal ebb and flow of commuters, but a succession of architectural styles starting in the Industrial Revolution, through the pomp of Victorian architecture, and extending forward into the most modern of structures.

A rebuilt station, especially one which is above the norm, is one of the modern symbols of regeneration to a community.

Stations bring all the daylit opportunities of highly glazed architecture and large overall roofs, as well as the safety challenges of minding the gap by day and by night, a risk-averse client, difficult mounting locations, 25kV overhead line equipment that needs respect, and a fairly grubby environment. If you like a lighting design challenge, light a station.

Architecture: gmp/ Photo: Marcus Bredt

Bob Bohannon tracks down his favourite railway stations

3 Stadelhofen Station, Zurich Santiago Calatrava is justifiably a starchitect, but Stadelhofen is on a smaller, more human scale to some of his epic works. A modest through-station on the Zurich S-Bahn, it uses his signature organic skeletal forms not just for the canopy supports, but for the catenary outriggers, a high-level walkway and a steeply graded overtrack bridge. It plays with form, structure, light and shade while weaving a busy station through a built-up area of town, never overwhelming, but deeply brilliant.

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Santiago Calatrava

Bob Bohannon is a past president of the SLL and head of policy and sustainability at the LIA

4 Canary Wharf, Jubilee Line Extension The first of two JLE stations in this personal Top 5, Foster + Partners' Canary Wharf is a space that induces feelings of awe and pride. Stations have been described as 'cathedrals of transport', but the nave here is a 300m-long underground cavern, making the view up to the escalators through the glazed arc to the heavens above all the more potent. It shares a lighting design element with St Pancras (both had input from Claude Engel): instead of a few larger uplights, the roof is lit by hundreds of small sources, so should one fail the overall scheme is not marred.

Berlin Hauptbahnhof Berlin Central Station is a mind-boggling, glittering symphony of glass and steel.

Everything about it is on another scale; it is over five levels and highly glazed so you can be looking at the roof of a train on the level above you reflected in the glazed transept roof, or looking down on to a train several levels below. The high-level east-west line spans the Berlin Spandauer canal and has a curving 321m-long overall roof, punching through two office blocks on the way.

Shutterstock

St Pancras Europe’s destination station, and a wonderful symbol of the circular economy. Protected from demolition by Sir John Betjeman (whose statue gazes up at the lights, or possibly George Barlow’s magnificent 1860 train shed), St Pancras was rebuilt to become the grand London terminus of Eurostar from Paris, Brussels and Amsterdam. It is a glorious space, by day or night, and one that truly shows that extra thought put into lighting creates an airportrivalling experience. Few now fly to Paris, so it’s a low-carbon project as well.

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Denis Gilbert

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5 Stratford Regional Station, Wilkinson Eyre Is Wilkinson Eyre’s station my favourite? If so, why?

Not because I was born five miles away, not because it delivers a stunning building to a community that needed a lift and not because it’s a fitting terminus to the many great works of the JLE. It is the shape: its roof soars like a high-tech silver aerofoil, ending in a south-east-facing brise soleil sheltering a huge curtain wall that floods daylight across a concourse which elegantly unites an otherwise complex interchange.

The large asymmetric uplights uniformly illuminate the roof, bodies perfectly reflecting its curving shape – a combination so good I joined the company.

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Events

2024

For details of all upcoming webinars, go to: www.cibse.org/societyof-light-and-lighting-sll/sll-events/upcoming-webinars-and-onlinecontent For previously recorded CPD webinars (including regional webinars), go to: https://www.cibse.org/get-involved/societies/society-of-lightand-lighting-sll/sll-events/on-demand-webinars-past-presentations

EVENTS LIGHT + INTELLIGENT BUILDING MIDDLE EAST 2024 Date: 16-18 January Venue: Dubai World Trade Centre https://light-middle-east.ae.messefrankfurt.com SURFACE DESIGN SHOW Date: 6-8 February Venue: Business Design Centre, Islington, London www.surfacedesignshow.com/ WORKSPACE DESIGN SHOW Date: 27-28 February Venue: Business Design Centre, Islington, London https://workspaceshow.co.uk/ LIGHT + BUILDING Date: 3-8 March Venue: Messe Frankfurt https://light-building.messefrankfurt.com DESIGN LONDON Date: 21-23 May Location: Clerkenwell www.designlondon.co.uk/ IALD ENLIGHTEN EUROPE 24 Date: 21-22 June Location: London www.iald.org

AVAILABLE WEBINARS INCLUDE SIMPLE STEPS TOWARDS SUCCESSFUL AND ENJOYABLE TEAM INTERACTIONS Speaker: David Webster, partner, Centre for Teams DIFFUSE CONVERGENCE Speaker: Guinter Parschalk, Studioix, Brazil Lighting designer Guinter Parschalk talks about his professional trajectory through visual communication, fashion, packaging design and product design, culminating with lighting design, which in his view is the area that unites all the previous ones EVIDENCE-BASED LIGHTING DESIGN FOR PEOPLE IN SMART CITIES Speaker: Dr Navaz Davoodian, senior lighting researcher at UCL. Hosted by Guy Kornetzki The webinar is designed to give people a deeper understanding of the importance of evidence-based lighting design that prioritises the wellbeing of people in creating smart cities. The aim is to stimulate critical thinking and inspire innovative solutions.

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