Newsletter Volume 10. Issue 6. Nov/Dec 2017
The Society of Light and Lighting
Part of the Chartered Institution of Building Services Engineers
CITY OF GLEAMING SPIRES The third Night of Heritage Light
FOR GOOD MEASURE Kit Cuttle develops his theory of metrics 1
Editorial
Secretary Brendan Keely FSLL bkeely@cibse.org SLL Coordinator Juliet Rennie Tel: 020 8675 5211 jrennie@cibse.org Editor Jill Entwistle jillentwistle@yahoo.com Communications committee: Gethyn Williams (chairman) Rob Anderson Iain Carlile MSLL Jill Entwistle Chris Fordham MSLL Eliot Horsman MSLL Mark Ingram MSLL Stewart Langdown MSLL Linda Salamoun MSLL Bruce Weil All contributions are the responsibility of the author, and do not necessarily reflect the views of the society. All contributions are personal, except where attributed to an organisation represented by the author.
Copy date for NL 1 2018 is 24 November Published by The Society of Light and Lighting 222 Balham High Road London SW12 9BS www.sll.org.uk ISSN 1461-524X © 2017 The Society of Light and Lighting The Society of Light and Lighting is part of the Chartered Institution of Building Services Engineers, 222 Balham High Road, London SW12 9BS. Charity registration no 278104
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Over the past few years there has been considerable discussion about how to communicate the importance of good lighting to the general public. In many ways it is not an easy message to get across. It’s often frustrating that people can be confronted with some pretty bad lighting or even no lighting at all and somehow see it as part of life’s furniture rather than something that could be improved. It has taken some disastrous PFI lighting schemes – frequently managing to turn streets into fair imitations of stalags – to stir the public consciouness, for instance. There has been a parallel discussion about how to draw young people into the profession. This one starts with a fundamental problem in that the vast
majority are unaware lighting could even be a profession. It seems in both cases, the solution starts with inspiration. As Night of Heritage Light gains momentum with a third event, this time in Oxford (see p5), it is clear just how high profile a lighting event can be. By combining with the Curiosity Carnival, the lighting schemes for Oxford’s most famous buildings attracted thousands of people, who couldn’t fail to be impressed and beguiled to see their city so transformed. And as Pockets of Light moves to its second year, the event now directly engages and educates children of all ages about lighting. Suddenly a career in the profession becomes a possibility. Of course it takes a lot of hard work. As Edison said, genius is one per cent inspiration and 99 per cent perspiration. But that one per cent is crucial. Jill Entwistle jillentwistle@yahoo.com Erratum
In Peter Boyce’s article Lighting in Flux (NL September/October), the captions for the graphs on spectral sensitivity on p6 appeared the wrong way round. Specifically, the figure with one peak is for foveal visual acuity and the one with two peaks is for the perception of large field brightness. Our apologies.
Current SLL lighting guides
SLL Lighting Guide 1: The Industrial Environment (2012) SLL Lighting Guide 2: Hospitals and Health Care Buildings (2008) SLL Lighting Guide 4: Sports (2006) SLL Lighting Guide 5: Lighting for Education (2011) SLL Lighting Guide 6: The Exterior Environment (2016) SLL Lighting Guide 7: Office Lighting (2015) SLL Lighting Guide 8: Lighting for Museums and Galleries (2015) SLL Lighting Guide 9: Lighting for Communal Residential Buildings (2013) SLL Lighting Guide 10: Daylighting – a guide for designers (2014) SLL Lighting Guide 11: Surface Reflectance and Colour (2001) SLL Lighting Guide 12: Emergency Lighting Design Guide (2015) SLL Lighting Guide 13: Places of Worship (2014) SLL Lighting Guide 14: Control of Electric Lighting (2016) LATEST SLL Lighting Guide 0: Introduction to Light and Lighting (2017) SLL Lighting Guide 15: Transport Buildings (2017) SLL Lighting Guide 16: Lighting for Stairs (2017) Guide to Limiting Obtrusive Light (2012) Guide to the Lighting of Licensed Premises (2011)
Secretary’s column
to confirm the details in the near future. The Lighting Knowledge Series: LightBytes has replaced the Masterclass. This new format of shorter-style presentations under the headings Design, Specify, Build and Future started in Manchester and will be travelling round the regions over the coming months. The Manchester event was very well received and you will gain a great deal of information to help you create better lit spaces and stay ahead of the competition. The details of future events can be found on the website and I thank the speakers – Les Thomas and Nick van Tromp (Fagerhult), Helen Loomes (Trilux), Roger Sexton (Xicato) and Steve Shackleton (Zumtobel) – for their input. This year’s guest speaker for all events is Carl Collins, CIBSE’s digital engineering specialist, who will tell you all you need to know about light and digital engineering, BIM. Carl also leads the new Society of Digital Engineering within CIBSE, and existing CIBSE members can join this society as an Affiliate free of charge through to the end of 2018. All details are on the CIBSE website. The next Lighting Knowledge Series events will be on 30 November in Dublin and on 25 January in Birmingham. See the Events page (p16) for more details of dates and venues. In the middle of October, SLL president Richard Caple and I visited Dubai and exhibited at Light Middle East, as well as hosting the second Ready Steady Light ME event. Many thanks to the members of the UAE region for visiting the stand, and we would also like to welcome the new members from the event. As we go to press, we look forward to PLD-C 2018 in Paris at the beginning of November and, of course, the finals of The Challenge speaker competition. Then it’s LuxLive at ExCel on 15-16 November where we will host the finals of the Young Lighter of the Year. We’re very much looking forward to that and hope to see many of you there. On 21 November we will be at the new CIBSE Build2Perform Live at Olympia London. The first morning of this twoday event – which is free to register and attend – will see the society host the Lighting Spaces: User Wellbeing and Performance session. The presentations and debates will include natural and artificial light coordination, design innovation and controls, and finally procurement for optimum performance. We’ll see you there.
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bkeely@cibse.org
Events
Secretary’s column
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News 4 Gleaming spires SLL president Richard Caple on the third Night of Heritage Light event in Oxford
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A procedure for change Following his LR&T lecture last month, Kit Cuttle develops his perception-based theory of lighting metrics
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Display of unity 12 Panos Andrikopoulos reports on the key themes and drivers for the International Museum Lighting Symposium and Workshops at UCL in September Clear vision 14 Colour and driving hazards are the two key themes in the LR&T papers selected by Iain Carlile Obituaries 15 Tributes to Mark Wood-Robinson and Alan Wilson Cover: the Museum of Natural History and Pitt Rivers Museum, one of seven historic Oxford buildings lit by SLL members as part of Night of Heritage Light III (see p5)
Dan Paton
Were you there in Oxford on the evening of 29 September? Night of Heritage Light III and Pockets of Light was delivered by the SLL’s brilliant volunteers (see p5). We had great input from the University of Oxford Estate Services and volunteers along with the Curiosity Carnival, and we did what we set out to do – showcase the skills and expertise of the society’s members, educate the young through school engagement and demonstrate to the public the powerful impact of light in the night-time environment. A huge thank you to the designers of the sites, the volunteers that planned and delivered the event and, of course, the suppliers, whose input was crucial. All suppliers, design teams and sites/ results can be seen on the project page of the SLL website. A special mention to Simon Fisher, Dan Lister and his team, and president Richard Caple. Earlier in the month we co-hosted the first Museum Lighting Symposium with SEAHA at UCL (see p12). The two-day event included 140 speakers and delegates from around the globe specialising in the field of museums and galleries. A big thank you to Panos Andrikopoulos, and Danny Garside from SEAHA, whom it was a pleasure to work with. We will be able to upload the video presentations from the event in the near future and will inform you once they are available to view. So that was September, and October was no less busy. The week starting 9 October saw the lecture from Kit Cuttle and the first of the Lighting Knowledge series: LightBytes event. The lecture from Kit at UCL was thoroughly inspiring (see p8) and a great way to start the celebrations of Lighting Research and Technology journal’s 50th-anniversary celebration in 2018. Planning is ongoing for the LR&T symposium on 16 May 2018 in London and we will be able
Contents
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NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...
Finalists chosen for YLOTY Award
Three finalists have been selected for this year’s SLL Young Lighter of the Year Award, with the finals again taking place at LuxLive, London ExCel, in November. The paper by Amir Nezamdoost (above left), a PhD student in architecture at the University of Oregon, is a case study and will examine Life Cycle Analyses, Annual Daylight and Energy Impacts of Manual and Automated Blinds. Seren Dinçel (above centre), who is
currently with Stockholm-based consultant ÅF Lighting, will present a paper called City Lighting in Scandinavia: design approach and methodology. Matt Hanbury (near left), founder of Dublin-based Lightly Technologies, will focus on Ultra-Thin Surface Light Sources: picking up where OLED stalled. Each of the finalists will deliver a 15-minute presentation in front of the judges and a live audience. The aim of the awards, now in their 23rd year, is to promote younger members of the lighting profession and raise their profile within the industry. The presentations will be at LuxLive on 16 November, with the winner announced at the Lux Awards
Cuttle gains doctorate from Dublin Institute Christopher ‘Kit’ Cuttle has graduated with a PhD from Dublin Institute of Technology in October at the age of 80. He completed his PhD by prior publication. Dr Cuttle has had a long and varied career in lighting. He has worked on daylighting at Pilkington Bros in the UK, taught illuminating engineering and, more recently, lighting design at the University of Wellington, New Zealand, where he lives.He was a researcher and academic at the Rensselaer Lighting Research Center in Troy, NY, and the University of Auckland, New Zealand, and is
also the author of two books on lighting. He developed a new approach to lighting metrics in 2010 and presented on its latest evolution in both London and Dublin last month (see p8). ‘Throughout his career he has been known for his willingness to push the boundaries of lighting metrics and this is evident in his current attempts to convert people away from performance to perception-based metrics,’ said Dr Kevin Kelly, head of School of Multidisciplinary Technologies at DIT, where further research into Cuttle’s theories is being undertaken. ‘It was this drive that led to a successful collaboration with DIT and the achievement of a PhD by publication,’ added Kelly.
On the lighter side... We continue the theme of lamps made out of weird stuff (see cod skin lamps NL July/August) with the mushroom mycelium shade. Apparently the material – the vegetative part of a fungus – is a thing, and Sebastian Cox is the latest designer to exploit its potential for furniture and lighting, combining it with wood. He has teamed up with researcher Ninela Ivanova, who has been looking into mycelium for the past seven years as part of a PhD at Kingston University, London. The lamp, on show at Design Frontiers in Somerset House, part of the London Design Festival in September, apparently has a suede-like texture. Probably not edible then.
CIBSE Southern Region teams relight history at Southampton’s oldest building CIBSE Southern Region recently held a mini Ready Steady Light event where competing teams illuminated different features of a historic Southampton building, writes Alan Tulla. Built in 1348, the Tudor House is the oldest building in the city, just a few hundred metres away from the centre. Organised by Samantha Pope, Laurie Socker and other members of the committee, the event involved five teams lighting five different spaces in the house and gardens, some areas of which date back to Norman times. Luminaires were supplied by the local representatives of iGuzzini, KB Lighting, Ledaz and Wila Lighting (including
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Casambi Technology). In all, 27 engineers attended from various local consultants and lighting design practices including Cooper Homewood, GJA, HCC, JPLD, KCS, MTA and TNG, as well as the SLL. Many participants were from the CIBSE Young Engineers Group and gained firsthand experience of illuminating a real building with working luminaires. The winning scheme was the fountain in the garden by the iGuzzini team, closely followed by the Attic (pictured left), lit by the Wila team, and the Air Raid shelter (Casambi Technology). The event was hugely successful and could provide an ideal model for other regions to adopt.
Events
Gleaming spires @sll100
Dan Paton
SLL president Richard Caple on the background to the third NoHL event, which this year brought Oxford’s most famous buildings to light
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One of the winning school designs for the quad at the Bodleian Library, by Owen from North Kidlington primary school
In the third event of its kind, Night of Heritage Light took place on 29 September in the city of Oxford. Designed to showcase the talents of SLL members and the lighting community, teams of lighting designers lit seven of the most famous historical buildings on the University of Oxford campus. NOHL III was conceived following a meeting with Rob Gregg, principal electrical engineer of Oxford University Estates. He wanted to create a temporary lighting scheme for the historic and hugely important Radcliffe Camera building, in the centre of Oxford. Rob was passionate about the fact that the Camera building should be illuminated so that the beautiful architecture could be showcased in the evenings as well as during the day.
‘Events like these truly bring out the best in our industry. A call to arms from manufacturers for lighting equipment resulted in a huge amount of kit for us to call upon and use on the night’ 6
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Further discussions took place between myself, Simon Fisher and Rob Gregg with the idea that this could be expanded into a Night of Heritage Light event similar to previous years. In those discussions it also became apparent that the Curiosity Carnival, which formed part of Oxford’s inaugural inclusion in the European Researchers’ Night, was due to run for one evening on 29 September. The Curiosity Carnival was part of a Europe-wide celebration, offering a programme of activities across the city that gave an opportunity to meet researchers, and discover how research affects and changes people’s lives. Night of Heritage Light and the Curiosity Carnival shared similar goals. A plan was forming... In discussions with the CC team, additional buildings were identified as sites for Night of Heritage Light. The quad of the Bodleian Library was also earmarked as a site to run the second Pockets of Light event, the Stem-inspired initiative focusing on the participation of local schools. While simultaneously selecting partner designers for the project, a total of seven sites were also identified and agreed as ideal NoHL sites:
Ashmolean Museum Museum of Natural History and Pitt Rivers Museum Radcliffe Camera Radcliffe Observatory
Photography: Dan Paton
Events
Clockwise from top left, the NoHL sites: Ashmolean, Radcliffe Observatory, Museum of the History of Science, Radcliffe Humanities
Radcliffe Humanities building Museum of the History of Science The Bodleian Library
In selecting partner designers, we chose design teams that were based locally in and around Oxford. Lux Populi, Hoare Lea Lighting, DPA Lighting and Iain Macrae from Wila Lighting are all local to the city. Faye Frankland from Enigma Lighting returned to ‘close the loop’ from the inaugural NoHL in 2015 where, for reasons out of her control, the site was pulled on the night. Designers also selected were Ross Ashton, from Projection Studio (projection mapping on the Museum of Natural History and Pitt Rivers Museum), and Dan Lister of Arup, who worked to deliver the Pockets of Light installations. This was the second Pockets of Light event to take place alongside NoHL (the first was the York event last year). Myself, regional lighting representative Sonia Pepperell and SLL secretary Brendan Keely delivered lighting workshops to City of Oxford College, St Gregory the Great secondary school and North Kidlington primary school, educating pupils about light and the lighting industry, and challenging them to come up with their own lighting designs for the quad of the Bodleian Library. We were able to talk about light and lighting to more than 70 students in total, which resulted in around 70 excellent designs. With a winning design eventually selected from each school,
they were then brought to life by a team of lighting experts. Events like these truly bring out the best in our industry. A call to arms from manufacturers for lighting equipment resulted in a huge amount of kit for us to call upon and use on the night. A massive thanks to all of them. A big thank you also to all of those involved in the event this year. Special thanks to Rob Gregg and the Oxford University Estates for having the vision to start the ball rolling, Lesley Paterson and the Curiosity Carnival team for allowing us to run the event concurrently with their own, and Richard Francis from Monard Electrical, who, rather importantly, kept us safe leading up to and during the event.
Equipment suppliers Acdc, Amerlux, Black Light, Casambi, Erco, iGuzzini, Innovation LED, Kingfisher Lighting, LED Lighting Solutions UK, LED Linear, Light Projects, LITE, LumenPulse, MaxiLED, Meyer, Optelma, Osram, Philips Lighting, Rako, Reggiani, Rose Bruford College, SGM, SILL Lighting UK, Stanley LED Lighting, Studio Due, THAT Event Company, Thorlux Lighting, Trilux, Tryka, Zumtobel
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LR&T lecture: lighting metrics
A procedure for change Following his recent lecture, Kit Cuttle develops his radical new approach to lighting metrics based on perception The lighting profession is poorly served by current lighting metrics. While the lighting industry has benefited from spectacular science- and technology-based developments in light sources and controls, the traditional techniques that guide much of lighting practice have remained moribund and locked into a pattern of thinking that evolved in the first half of the last century. It was in 1920 that Ward Harrison and Earle Anderson presented their paper, Coefficients of Utilisation1, at the annual conference of the IES of North America. This paper established the basis of what we now refer to as the lumen method, which calculates the average illuminance on the horizontal working plane (HWP) and is, to this day, the recognised procedure for ensuring compliance with interior lighting standards. Although we now refer to the coefficient of utilisation as the utilisation factor, its function remains unchanged, and Harrison and Anderson defined it as ‘the proportion of useful lumens’1, meaning that any lamp lumens not incident on the HWP are useless and wasted. This notion was challenged early in the second half of the last century. In 1954, JM Waldram noted in his classic paper introducing the Apparent Brightness Design Method that ‘there has been a revolution in thought in interior lighting in the past eight years’2, and he went on to describe how thinking among lighting practitioners was turning towards the concept of brightness engineering to achieve ‘the design of the visual field’2. Eleven years later RG Hopkinson made a proposal for a future edition of the IES Code in which specified minimum task illuminance values would be replaced by schedules of luminance values, and noted that ‘the lighting of the building interior should not have to be constrained by lighting on any specific visual task, and should be planned in relation to the design of the whole building’3. The mid-years of the last century were a period of lighting surveys and research studies of brightness/luminance relationships (see for example, Marsden4), buoyed by a sense of optimism within the lighting community and confidence that lighting practice was about to change for the better.
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Now fast forward to the current edition of the SLL Lighting Handbook, and in the section on office lighting we find, ‘unless specified otherwise, the recommended maintained illuminance is measured on a horizontal plane at desk height’5. For interior lighting design, discussion of brightness has become restricted to provision for visual comfort (in other words, the avoidance of discomfort) and generally luminance is regarded as an unnecessary complication. However, before we attribute this abandonment of a vision for advancing lighting practice to lethargy, not everyone had been convinced that luminance was the answer. It was in 1971 that both PA Jay6 and JA Lynes7 expressed their concerns over the lack of attention given to the role that the visual constancies play in perception and, in particular, to the role of lightness constancy. Providing that we are in an environment that is sufficiently illuminated to enable surfaces and objects to be readily recognised, lightness constancy is the phenomenon by which an object, such as a sheet of white paper, is perceived to retain its lightness (the whiteness of the paper) whether it is in a more brightly lit or dimly lit location. We have no difficulty in distinguishing between relatively brightly lit, low-lightness surfaces and more dimly lit, high-lightness surfaces, even if they have similar luminance values. As PR Boyce has recently commented, ‘this ability to separate illuminance from reflectance under most lighting conditions makes the use of luminance as the basis of lighting design criteria problematical’8. For the practitioners who engage in determining interior lighting solutions, the implications of this observation are profound. The lightness values (which are related to reflectance) of the surfaces and objects that make up the locations where lighting is to be applied are predetermined, and the variable that the lighting practitioner controls, illumination, is perceived largely (but not completely) independently of lightness. Luminance, by confusing lightness and illuminance, fails to provide useful information of how lighting influences the appearance of lit surroundings (although it has other uses, such as for visual performance analysis). It follows that the most useful metric for planning interior lighting installations is illuminance: but not the illuminance metric that we are accustomed to. It is sobering to consider the extent to which the almost-century-old horizontal working plane concept dominates the thinking of today’s lighting practitioners. If a colleague
‘Discussion of brightness has become restricted to provision for visual comfort and luminance is regarded as an unnecessary complication’
Figure 1: approaching the Winged Victory of Samothrace sculpture in the Louvre. A distinct luminance contrast is created by displaying this dark object against a lighter background. While this creates a striking silhouette from a distance, it does not fully reveal the object’s visual characteristics
Figure 2: Close to, the appearance of the statue is beautifully influenced by selective lighting. It reveals the statue’s form and texture, and provides for visual emphasis. It may be noted that this lighting has the effect of reducing the object/background luminance ratio, while raising the target/ambient illuminance ratio
hands you a light meter and asks you to assess the light level wherever the two of you happen to be, then, regardless of whether you are in a work-related location, would you even think twice before holding the meter horizontally at around waist-height to take a reading? Two illumination concepts are proposed for determining how lighting affects the appearance of an illuminated indoor space. These are:
These two concepts and their associated metrics, MRSE and TAIR9,10,15, are the subject of ongoing research at the Dublin Institute of Technology, which so far has addressed issues of calculation and measurement11, and relationships between brightness assessment and MRSE12,13. It is anticipated that this work will lead to defined functional relationships relating visual assessments to these metrics, and so providing a robust research basis for specifying lighting design objectives. To appreciate the relevance of these metrics to lighting practice, imagine that you are on a trip to Paris and you are visiting the Louvre, and as you walk around a corner, you come face-to-face with the architectural experience shown in Figure 1. Your eye is unerringly drawn towards the thirdcentury BCE Greek statue, the Winged Victory of Samothrace, and as you approach this masterpiece of the ancient world (Figure 2), you become aware of the skill with which the sculptor has captured a frozen instant of a moving three-dimensional form, and has revealed the soft folds of fabric in stone. It takes a lighting nut to recognise the skilful application of selective target illumination on to this dark object, which reduces the luminance contrast relative to its background, while imparting
Ambient illumination, being the diffusely inter-reflected light field within the volume of an enclosed space. The associated metric is mean room surface exitance (MRSE)9, being the average exitance (lm/sqm) of the surrounding room surfaces and objects that form the boundaries of the light field. Target illumination, being the sum of direct and ambient illumination incident on selected target surfaces. The associated metric is target/ambient illuminance ratio (TAIR)10, being the ratio of target illuminance to MRSE.
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LR&T lecture: lighting metrics
LR&T lecture: lighting metrics
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Figure 3: this supermarket lighting provides ambient illumination, which lights everything in general and nothing in particular
Figure 4: target illumination creates visual emphasis for a product display by raising the target/ambient illuminance ratio
visual emphasis by raising the target/ambient illuminance ratio. We do not need to restrict ourselves to such esoteric situations in order to experience these effects. Figure 3 shows a corner of my local supermarket in Wellington, New Zealand. To determine how much illumination should be provided in this situation, the conventional approach is to ensure that illuminance sufficient for efficient performance of the critical visual task is provided on the task plane. The problems of attempting to apply such a process in this situation are obvious, and instead, a practical approach would be to recognise that the function of this lighting is to provide ambient illumination to create an overall sense of surrounding brightness. The functional relationship that remains to be defined is: surrounding brightness/MRSE. Walking through the store presents a different situation. Figure 4 shows target illumination has been added to the ambient illumination to give visual emphasis to a selected product display. Again, to analyse this situation in terms of luminance ratios would be quite impractical, and we note that in this case, the lighting achieves its effect through raising the target illuminance above the ambient level. The functional relationship that remains to be determined is: visual emphasis/TAIR. Whether we are dealing with a temple of high art or an everyday retail outlet, application of these lighting concepts may be facilitated by use of the lighting design objectives – direct flux distribution procedure (LDO-DFD)14, the outline of which is charted in Figure 5. There are several novel aspects of this procedure to be noted. The conventional approach, using the lumen method, starts with choosing a luminaire, and progresses through determining a layout to calculating the lamp lumens needed to provide the specified HWP illuminance. Waldram reversed that sequence, starting by specifying the lighting design objectives and leading to determining the lamp/luminaire layout needed to achieve the objectives. That is the procedure employed here, although there are distinct differences from Waldram’s designed appearance method. Users of this procedure have the choice of prioritising their
decision making for illumination efficiency, or for illumination hierarchy. The efficiency track is concerned with optimising the utilisation of luminous flux to satisfy peoples’ expectations for adequate ambient illumination, and the hierarchy track is concerned with balancing ambient illumination with an ordered distribution of target illumination. For either track, the required ambient illumination is specified in terms of MRSE, and the target illumination in terms of TAIR. The outcome is a direct flux distribution, being a specification of the lumens to be provided by the luminaires on to selected surfaces that will, allowing for inter-reflection of light within the volume of the space, provide the level of ambient illumination
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‘Luminance, by confusing lightness and illuminance, fails to provide useful information of how lighting influences the appearance of lit surroundings’ and the balance of target illumination to satisfy the lighting design objectives. How the LDO-DFD procedure may be facilitated by use of a spreadsheet is described in my book, Lighting Design: A perception-based approach15. (The spreadsheets may be freely downloaded by going to www.routledge.com/books/details/9780415731973/ and clicking on eResource/Downloads.) For these opportunities to become available in general lighting practice would require minimum illumination standards for specific applications to be specified for the perceived adequacy of illumination (PAI) criterion, being the ambient illumination level to satisfy a nominated proportion of people for surrounding brightness, specified in MRSE values. In this way, the specified minimum illumination level would be
LR&T lecture: lighting metrics
Figure 5: the lighting design objectives – direct flux distribution (LDO-DFD) procedure, illustrating the design progression sequence for ambient and target illumination, prioritised for illumination efficiency or hierarchy
the ambient illumination level below which an unacceptable proportion of the occupants of a space would regard it as appearing insufficiently bright for the activity it houses. It is not proposed that TAIR values should be regulated. It may be seen that the LDO-DFD procedure is less than a lighting design process. It requires as its starting point the development of lighting design objectives, some of which are to be specified in terms of MRSE and TAIR. From these specified values, the procedure guides practitioners through prioritising their objectives for illumination efficiency or illumination hierarchy, to achieve a direct flux distribution. This distribution specifies the direct flux to be directed on to selected target surfaces to achieve, after inter-reflection, the required levels of ambient and target illuminances. The development of the lighting installation involves selection of luminaires with flux distributions suitable for the direct flux distribution. Conventionally, the role of luminaires is seen to be to gather the light source flux and to direct it on to the horizontal measurement plane, whereupon the quest for efficiency inevitably leads to selection of downlighting luminaires. The LDO-DFD procedure involves a different understanding of the purpose for providing illumination, for which the luminaires’ direct flux on to room surfaces then becomes a secondary luminaire, creating light distributions that relate lighting practice to human assessment of the visible effects of illumination. A Fresh Approach to Interior Lighting Design: an Exitance-based Procedure was the title of a lecture delivered by Kit Cuttle at UCL on 10 October. The event marked the start of celebrations for the 50th anniverary of Lighting Research and Technology (LR&T) in 2018
References
1 Harrison W and Anderson EA. Coefficients of utilisation. Trans IES (New York) 1920; 15: 97-123. 2 Waldram JM. Studies in interior lighting. Trans Illum Eng Soc (London) 1954; 19: 95-133. 3 Hopkinson RG. A Proposed Luminance Basis for a Lighting Code. Trans Illum Eng Soc (London) 1965; 30(3): 63-88. 4 Marsden AM. Brightness – A review of current knowledge. LR&T 1969; 1(3): 171-181. 5 SLL Lighting Handbook, 2009. Office Lighting. London, CIBSE. 162. 6 Jay P. Lighting and visual perception. LR&T 1971; 3(2): 133-146. 7 Lynes JA. Lightness, colour and constancy in lighting design. LR&T 1971; 3(1): 24-42. 8 Boyce PR. Human Factors in Lighting. 3rd ed. London: CRC Press, 2014, p83. 9 Cuttle C. Towards the Third Stage of the Lighting Profession. LR&T 2010; 42(1):73-93. 10 Cuttle C, A New Direction for General Lighting Practice. LR&T 2013; 45(1): 22-39. 11 Duff J, Antonutto G and Torres S. On the calculation and measurement of mean room surface exitance. LR&T 2016; 48(3): 384-388. 12 Duff J, Kelly K and Cuttle C. Spatial brightness, horizontal illuminance and mean room surface exitance in a lighting booth. LR&T 2017; 49(1): 5-15. 13 Duff J, Kelly K and Cuttle C. Perceived adequacy of illumination, spatial brightness, horizontal illuminance and mean room surface exitance in a small office. LR&T 2017; 49(2): 133-146. 14 Cuttle C. A fresh approach to interior lighting design: the design objective – direct flux procedure. LR&T Sept 2017; (Accepted for publication.) 15 Cuttle C. Lighting Design: A perception-based approach. Abingdon: Routledge, 2015.
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Events
Panos Andrikopoulos reports on the recent Museum Lighting Symposium and Workshops in London, which brought together people from diverse disciplines to discuss lighting for both the present and posterity
Museum lighting is like no other lighting field. Or any other vision, colour, conservation or material science field. Museum lighting involves many disciplines and an even greater number of stakeholders: lighting designers, architects, exhibition designers, conservators, and material, vision and lighting scientists, to name a few. All these practitioners approach the field with different perspectives, interests, backgrounds and methods, and they each employ a subtly different professional language. This can lead to miscommunication and isolation. The delegates of the 1st International Museum Lighting Symposium and Workshops met to address exactly this, bringing together industry professionals, scientists, and academics working in the field of museum lighting. Museum and gallery lighting is at a crossroads. The drive to reduce energy consumption has led to a wide and rapid adoption of LED technology by museums and heritage institutions. Solid state lighting creates new opportunities but also poses new challenges. While it allows for novel applications such as optimisation of the spectrum for vision and/or preservation, it has revealed inadequacies in existing colour reproduction measures, has not yet proven to be cost effective, and has raised concern over light-induced damage. Projects such as the recent illumination of the Sistine Chapel, where the light source was specifically optimised for the particular pigments used for the murals, showcase the potential of LED technology, but also highlight the need for engineering its capabilities. The idea for a museum lighting event was
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conceived with all of these issues in mind. We envisaged a symposium acting as a round table for all the disciplines involved in the field, whether within industry or academia. A showcase where industry professionals would be able to discuss state of the art research in order to apply it in the real world, and where researchers would be able to learn more about the challenges of real-world application. The programme, and the demographics of the audience, suggest that these aims were met. The audience was diverse: 26 per cent were museum professionals, 24 per cent came from academia, 23 per cent were lighting manufacturers, and 15 per cent were lighting designers and specifiers. Delegates came from the UK, USA, Germany, Italy, Belgium, Norway, Greece, Portugal, China, Japan, Singapore, Argentina and Egypt. This split, along with the fact that the event has been twice sold out long before the actual date, demonstrates a great and growing interest in this field from all stakeholders, and a community in the making.
‘Museum and gallery lighting is at a crossroads...LED technology creates new opportunities but also poses new challenges’
Danny Garside
Display of unity
Events
‘UCL Museums and Collections provided the opportunity to host some of the workshops in real museum environments’ David Saunders, vice president of the International Institute for Conservation, gave a fascinating overview of research in the field of wavelength dependence of light damage. The second keynote speaker, Stefan Michalski, senior conservation scientist with the Canadian government, summarised 30 years of developments in museum lighting (since the last big museum lighting conference, in Bristol). Prof Anya Hurlbert, Sergio Nascimento, Peter Bodrogi and Ferenc Szabo talked about colour and the effect of colour temperature in colour appearance and preference. Apart from the presentations, the programme included four workshops provided in association with lighting manufacturers. Outside the norm of conferences being sponsored by lighting companies, this event did not have sponsors; rather it had commercial partners. While this might sound like sophistry, it is in fact a pertinent distinction. While their financial support was key to the success of the event, this was far from their only contribution. Commercial partners organised workshops, demonstrating state-of-the-art technology and knowledge, significantly contributing to the knowledge wealth of the event. As a result of this, the programme included four workshops. Workshop A: Relighting the Petrie Museum: smart lighting and proximity aware services in museums (organised with Xicato and Mike Stoane Lighting, and led by Boris Pretzel, head scientist at the Victoria and Albert Museum) was not only a demonstration of the capabilities of connected lighting in museum environments, but also an open discussion on the potential of the technology. Workshop B: Precision LED Drivers for Viewing and Digital Imaging (provided by eldoLED, and presented by Scott Geffert, senior imaging manager of New York’s Metropolitan Museum of Art, and Gé Hulsman from Eldo) was a demonstration of the implications and importance of dimming LEDs in museums and the applications of controllable LEDs in imaging. Workshop C: Psychophysiological Methods for Lighting Research and Design (provided by Zumtobel and organised in the Grant Museum of Zoology, led by Prof Anya Hurlbert, Panos Mavros of the Future Cities Laboratory of ETH, and myself) introduced new methods and techniques to be employed for
post- and pre-occupancy evaluation of designs and lighting conditions. Workshop D: Modern Colour Science for Museum Lighting (provided by Soraa and Coco Lighting, and led by Soraa’s Aurelien David) discussed all the latest advances in modern colour science and colour rendering. Museum lighting research usually happens in the lab, outside of its real context. Although this is not ideal, it is often a pragmatic decision. Depending on the application, the importance of lighting research in situ is widely acknowledged. For this event, UCL Museums and Collections provided the opportunity to host some of the workshops in real museum environments. This aligned well with the aim of UCL Museums and Collections to become a ‘museum research hub’. As a legacy of the Museum Lighting Symposium, a lighting system, which is optimisable up to the last spotlight and with the ability to track the location of visitors, has been installed in the Petrie Museum. This system is open to UCL students as well as UCL and non-UCL researchers for lighting studies. When initiating the symposium, we hoped to instigate a conversation, a dialogue between different fields and practices. While we feel we have contributed significantly to that cause, because many people were not able to participate in the event, either due to travel costs or because it was sold out two months before the actual date, we will be setting up a Museum Lighting meet-up and email group to keep the conversation open until the next event. You can sign up for our mailing list on the website (https://museumlightingconference.com). We are also strong believers in open access, and so we have made the book of abstracts freely available for download on the website. Video recordings of many of the presentations will be made available in the weeks to come, announced through our mailing list. The International Museum Lighting Symposium and Workshops took place from 11-12 September at UCL. It was organised by UCL PhD researchers with the support of the SLL and the Centre for Doctoral Training in Science and Engineering in Arts, Heritage and Archaeology (SEAHA). Chair of the organising committee, Panos Andrikopoulos is a PhD researcher at the UCL Institute for Sustainable Heritage and the UCL Colour Vision Research Laboratory, and a lighting scientist at ACT Lighting Design
Norbert Miguletz
The programme featured 21 presentations. Keynote speaker Florence Lam, global lighting leader at Arup, spoke about lighting the Acropolis Museum. Andreas Schulz, founder and principal of Licht Kunst Licht, looked at daylighting and the application of novel lighting design in museums such as the Städelsches Kunstinstitut in Frankfurt and Kunstmuseum Ahrenshoop in Berlin. Kerri Callahan, director of Architectural Project Management and Planning at the Art Institute of Chicago, described the implementation of colour tuneable LED lighting systems.
Opposite: keynote speaker Florence Lam on Arup’s lighting scheme for the Acropolis Museum. Above: the daylit interior of Städelsches Kunstinstitut, Frankfurt, one of the projects discussed by speaker Andreas Schultz of Licht Kunst Licht
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LR&T essentials
Clear vision Iain Carlile finds chromaticity and driving hazards are the two key topics of the latest LR&T papers The latest published Lighting Research and Technology papers focus on the topics of colour and road lighting. In the first of the papers on colour, Royer et al examine how a person’s perception of light source colour quality is dependent on the source’s colour rendition and chromaticity. An experiment was conducted in which the participants evaluated different lighting scenes in rooms filled with objects. The lighting scenes included five chromaticity groups with 10 systematically varied colour rendition conditions in each group, giving 50 different lighting scenes in total. Participants rated each scene on eight-point scales for saturated-dull, normal-shifted and like-dislike. In addition participants selected whether they personally found the scene acceptable or unacceptable. According to the findings of their investigation, the authors suggest that perceptions of colour rendition can vary with chromaticity. They also propose that IES TM-30-15 measures can be used to predict perceptions of normalness, saturation, preference and acceptability in a polychromatic architectural environment. Minor differences in the models were observed at different colour temperature (between 2700K and 4300K) and Duv combinations. Also considering colour, Esposito and Houser propose a novel measure of colour discrimination for light sources, Rd, which is used to quantify the number of cap transitions in e FM100 (Farnsworth-Munsell 100 Hue Test) introduced by the spectrum of a light source. The authors developed Rd using data from an experiment in which 20 participants undertook FM100 tests under 24 different light sources. The spectra of the light sources used were systematically varied in IES TM-30-15 Rf (fidelity index), Rg (relative gamut-index), and gamut shape. From their study the authors show that a larger gamut area is not associated with better colour discrimination. This was especially true in light sources with sharp peaks in their SPD (spectral power distribution), as is common with many LED light sources. Turning to the lighting of roads, the first paper looks at how the presence of fog leads to an increase in traffic accidents. Fotios, Cheal and Uttley undertook an experiment to investigate how changes in peripheral vision hazard detection were affected by changes in road surface luminance, scotopic/ photopic (S/P) ratio and density of fog. Reactions to two different hazards were measured: a road surface obstacle and another vehicle changing lane. From the study it was found that an increase in luminance and reduction in fog density led to a significant increase in reaction time of detecting hazards. An increase in S/P ratio was
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Percentage of participants for which a colour was ranked in the top three based on having the most influence on the participant’s judgements (Human perceptions of colour rendition at different chromaticities, Royer et al)
only significant in detecting the road surface obstacle under thick fog, leading to a faster reaction time. A second paper by Fotios, Cheal and Uttley also investigates driving hazards.An experiment was undertaken to investigate the peripheral detection performance of a driver during transitions between lit and unlit sections of road. The experimental results suggested that a driver’s performance decreases almost immediately when moving from a lit to unlit section of road and no significant change in performance was made in the following 20-minute period of time. In contrast, when moving from an unlit to lit section of road the increase in performance is almost immediate with no further change with time. It was found that a small amount of road lighting (0.1 cd/sqm) improved detection compared with no road lighting. Increasing road luminance to 1.0 cd/sqm further increased hazard detection, but an increase to 2.0 cd/sqm did not suggest further benefit. Detection performance between S/P ratios of 0.65 to 1.40 (at 1.0 cd/sqm) demonstrated no difference. From the results the authors conclude that, in the current context, visual performance plateaued at a road luminance of 1.0 cd/sqm. Iain Carlile, MSLL, is an associate of DPA Lighting
Lighting Research and Technology: OnlineFirst In advance of being published in the print version of Lighting Research and Technology (LR&T), all papers accepted for publishing are available online. SLL members can gain access to these papers via its website (www.sll.org.uk) Human perceptions of colour rendition at different chromaticities MP Royer, A Wilkerson and M Wei A new measure of colour discrimination for LEDs and other light sources T Esposito and K Houser The effect of fog on detection of driving hazards after dark S Fotios, C Cheal, S Fox and J Uttley The transition between lit and unlit sections of road and detection of driving hazards after dark S Fotios, C Cheal, S Fox and J Uttley
Obituaries
Two past chairs of the Lighting Division (as the SLL was formerly known), Mark Wood-Robinson and Alan Wilson have sadly died within weeks of each other.
Mark Wood-Robinson Mark Wood-Robinson specialised in church lighting – he lit many churches in the south west, and the cathedrals in Exeter, Wells, Bath (Abbey) and Bristol – which reflected his strong religious beliefs. Born and educated in India, he came to London after the Second World War. He gained a City and Guilds diploma in lighting engineering before working for lighting company Echo and also for the Electricity Council in London. He went on to become a lighting consultant for SWEB in Bristol. In the late 1950s he was on a technical committee at ELFA (Electric Light Fittings Association), which subsequently evolved into the LIF in 1969. The author of many articles and technical reports, he was a keen supporter of the CIE and at one time was its UK representative. He was chair of the CIBSE Lighting Division from 1982-83. ‘He was an excellent lighting designer and an expert in church lighting,’ said Lou Bedocs, one of many who paid tribute. ‘He was a wonderful man, easy to get on with, and an excellent CIBSE Lighting Division chair. I feel that lighting has lost a great champion.’ ‘He will be remembered by many as a charming and courteous man, whose generous sharing of his wisdom and knowledge shone through his unassuming demeanour,’ said Hugh Ogus. He was the epitome of a true gentleman, said Iain Maclean, ‘and an excellent engineer with a great sensitivity for the architecture of many of our historic church buildings’. He was also an innovative thinker, said Bob Venning. ‘He pioneered the concept of IED, which was a 1970s attempt at integrated design for the comfort of the occupants while reducing the overall energy consumption. It had many merits but led the way to a better understanding of how lighting was an integral part of a building design. Yes he was a gentleman, but he was a sound thinker about lighting matters too.’
Alan Wilson A consulting engineer and designer, Alan Wilson was chair of the CIBSE Lighting Division from 1991-92. He worked for many years both at national level and in the North West Region. He played a major part in the preparation of the 1994 edition of the Code for Interior Lighting, particularly the General Schedule. He also chaired the task group which prepared an edition of a Lighting Guide on the industrial environment. He was chair of the CIBSE North West Region (and before that of the IES Manchester Centre) and served for many years on the regional committee. He played a major part in organising regional events in the Manchester area and was the retired diocesan adviser on lighting for the Diocese of Manchester. He was also highly committed to education. As well as lecturing on lighting at courses run at UMIST, he was very supportive of CIBSE Lighting Division activities targeting young people in lighting. ‘He was a knowledgeable engineer and a very good person to work with,’ said Geoff Levermore. ‘A lot of students benefited from his wisdom, help and humour.’ ‘He was passionate about lighting education and I benefited from his wisdom in the early days of the Lighting Education Trust as well as from his help during the development of the Lightmongers’ Education Awards programme,’ said Hugh Ogus. ‘He made an important contribution to our profession and is a great loss.’ Anthony Ormsworth was one of many others who paid tribute. ‘I will always remember Alan as being a kindly person, who made one very comfortable and feel respected. I had the greatest respect for him as a very competent “lighter” who was always willing to share his outstanding knowledge. The world will be a poorer place without him, and for the SLL it is the loss of one of the “old brigade” who helped to bring the society to the prominent position it now holds.’
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EVENTS...EVENTS...EVENTS...EVENTS...EVENTS...EVENTS...EVENTS...EVENTS...EVENTS...EVENTS...EVENTS
2017 1-4 November Professional Lighting Design Convention (including The Challenge competition) Venue: Palais des Congrès de Paris http://pld-c.com 15-16 November LuxLive 2017 Venue: London ExCeL http://luxlive.co.uk 16 November Young Lighter of the Year Final Venue: LuxLive, London ExCel www.sll.org.uk 16 November Lux Awards 2017 Venue: InterContinental London – The O2 http://luxawards.co.uk 21 November Lighting Spaces: User wellbeing and performance (Organised by CIBSE/SLL) Speakers include: John Mardaljevic, Iain Macrae, Helen Loomes Chair: Iain Carlile, DPA Lighting Time: 10.30am-12.30 Venue: Olympia, London (Build2Perform, see below) www.sll.org.uk 21-22 November Build2Perform (CIBSE event, formerly Building Performance Conference and Exhibition) Venue: Olympia, London www.build2perform.co.uk 24 November Lighting: legislation and energy efficiency (CIBSE training course) Venue: CIBSE, Balham High Road, SW12 www.cibse.org 30 November SLL Lighting Knowledge Series: LightBytes Venue: Teeling Distillery, Dublin sll@cibse.org 30 November How to be Brilliant: with Smoke and Mirrors (Organised by the ILP) Speakers: Graham Rollins and Ingo Kalecinski, GNI Projects Venue: Marshalls Design Space, EC1 jess@theilp.org.uk 4 December Artificial Intelligence: SLL event in association with Arup exhibition Venue: Arup, 8 Fitzroy Street, W1 sll@cibse.org
15-16 November: LuxLive at London ExCel, including YLOTY final
8 December Lighting Design: principles and application (CIBSE training course) Venue: CIBSE, Balham High Road, SW12 www.cibse.org
Lighting Knowledge Series: LightBytes The Lighting Knowledge Series is kindly sponsored by Fagerhult, Trilux, Xicato and Zumtobel. For venues and booking details: www.sll.org.uk
2018 23 January SLL and CIBSE Southern: Non-visual Responses to Light Speaker: Prof Debra Skene Venue: Holiday Inn, Eastleigh, Hants sll@cibse.org 25 January SLL Lighting Knowledge Series: LightBytes Venue: Birmingham Botanical Gardens sll@cibse.org 2 February Lighting: legislation and energy efficiency (CIBSE training course) Venue: CIBSE, Balham High Road, SW12 www.cibse.org 22 February SLL Lighting Knowledge Series: LightBytes Venue: We the Curious, Bristol sll@cibse.org 12-13 April CIBSE Technical Symposium: Stretching the Envelope Venue: London Southbank University www.cibse.org 16 May International Day of Light Including LR&T symposium (details tbc) www.lightday.org/www.sll.org.uk
LET Diploma: advanced qualification by distance learning. Details from www.lightingeducationtrust.org or email LET@cibse.org 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 training@thelia.org.uk For up-to-date information follow us on Twitter @sll100