Light across Disciplines and Times: A Walking Seminar at the Stockholm Public Library

Lighting in buildings today is a multi-disciplinary task. Increased complexity and specialization have led to a split process where coordination between disciplines is lacking. Despite extensive technical development, daylight and electric light are still planned in separate processes, often resulting in over-lit environments where energy savings, health and spatial potentials of daylight are not fully utilized. To address these problems, this paper introduces the walking seminar as a method to bridge and increase knowledge across disciplines in the field of lighting. The seminar was held at the Stockholm Public Library, and included invited participants with different professions and expertise: an architect, an electrical consultant, a lighting designer, a librarian, a caretaker, and an architectural historian who shared their perspectives on light. Based on the seminar, findings relevant for today’s practice are presented, both for the specific case in itself, a listed building and an active library, and at a more general level concerning lighting standards and the interaction of daylight and electric light. The main future task for the building sector is to preserve and develop our existing building stock, which includes lighting. Sustainable and long-term solutions require that daylight, electric light and spatial lighting design are planned as an integrated whole, based on the characteristics of the specific building. Findings from the walking seminar presented in this paper point at the importance and potential in transdisciplinary dialogue to enable the development of long-term lighting solutions in our existing and future buildings.


Introduction
This paper addresses the theme of knowledge transfer [1] between different groups of expertsspecifically, those working with lighting within the building sector.One reason, I hypothesize, for the unsynchronized way in which the planning processes handle lighting at present is the lack of collaboration and coordination occurring between different disciplines.The language available to communicate about lighting, further, is often discipline-specific and as such insufficient in accessing the full potential of the field of lighting design.
In practice, the design of lighting takes place during different stages of the building process.The basic conditions for daylight in new buildings are set early on in the planning stage; these conditions are then developed further by architects and environmental specialists who carry out energy and daylight calculations.In contrast, electrical lighting is planned by the lighting designer and/or by the electrical engineer during the final stage of building design.The maintenance and development of the existing building stock constitutes the main task for the building sector at present and presumably also in the future); because electric lighting is changed more often than other aspects of a building and large transitions like the introduction of LED have occurred, the field has rapidly transformed in recent years.

The Walking Seminar as a Method
In their work on inventive research methods, Cecilia Lury and Nina Wakeford argue that "a method must be made specific and relevant to the problem posed.In short, inventive methods are ways to introduce answerability into a problem."[2] In the case presented here, the walking seminar was chosen as a method in order to make visible different specialist groups involved in lighting in buildings, to understand and identify critical issues in current lighting design, and to highlight and bridge gaps in communication between different perspectives on light.
In existing buildings, electrical lighting is often treated as a secondary technical installation, without considering its spatial and visual effects.If a broader approach is to be developed, multiple competencies and perspectives are required, and (as with other issues in architecture based on teamwork) collective research methods that are designed for group reflection are necessary.Moreover, the visual impact of light must be explored within specific spatial situations.Given these requirements, walking seminarswhich involve the design of a series of temporal spatial situations in which participants meet and move together and where each new situation relates to (and is visually impacted by) that which has been experienced previously-are highly relevant.
The Stockholm Public Library, which was chosen as the location for the seminar, is not only an active public library but a well-known cultural historical building designed by Gunnar Asplund, which is often referred to in relation to its lighting design.[3] The library is an interesting example of the encounter between older, daylight-based lighting design and contemporary approaches, whereby the electrical lighting scheme was added over time, giving it an overlapping but not coherent character.Fulfilling contemporary needs in buildings whose lighting stems from another age, when other conditions and ideals prevailed, constitutes a complex task.I argue, in listed buildings, such as the Stockholm Public Library, original luminaires are to be preserved, but the effect of light is not.[4] This raises interesting questions about the role of light and who/what controls and governs its spatial design: What qualities are important to preserve and what may need to change when modernizing lighting in older buildings?How can these values be identified and communicated?
As a doctoral student (DS), I designed and organized the walking seminar as part of my thesis, extending from my previous long experience as a practicing architect and lighting designer.The overall theme of the seminar was "lighting" as it is seen from different perspectives; those perspectives were represented by the invited participants, who were carefully selected based on their diverse experiences and backgrounds.The participants were: a caretaker (C) and a librarian (L), whose long experience working in the library had given them a high level of insight into the daily activities that occur there; a lighting designer (LD) with a background in architectural education and research; an architectural historian (AH) with specialist knowledge of the building; and an architect (A) with expertise in heritage buildings and an electrical consultant (EC) with experience working with heritage buildings, both of whom were involved in ongoing maintenance work at the City Library.The participants were informed and gave their consent via email to be part of the research, and to be recorded and cited in publications.The recordings were transcribed and edited by me.The text was revised according to the comments from the participants, none of whom requested anonymity.The seminar was designed as a walk through the library with a number of stops linked to various themes that touched on different aspects-technical, practical, and spatial-of light, represented by the different perspectives of the participants.The seminar moved between different time periods, reflecting upon the technical innovations and legislative changes that had affected the building's lighting scheme since its construction in 1928, the same year that the frosted incandescent was introduced to the Swedish market.

The Walk
In the following section I present the conversation that occurred on our walk through the library, structured in terms of the five stops that were made, each of which had a different theme, see Figure 1.Themes and questions were sent to the participants in advance for their preparation.Questions were deliberately designed to enable an open dialogue between the participants and allow for each participant's perspective.[5] The conversation is presented as a curated summary based on transcripts, written in quotes in present tense.The ambition is to highlight knowledge that is of interest for the specific case, as well as knowledge that is relevant to lighting in general.

The Storytelling Room-An Introduction to the Walk and a Presentation of the Participants
(DS): Welcome all participants!The Storytelling Room is the first stop on our tour through the library.During the seminar, we will have the opportunity to share perspectives on light and to move between different time periods, reflecting on historical changes in the lighting of the building.The Storytelling Room has largely remained unchanged since the library was opened in 1928, with the exception of the electric lighting, which originally consisted of only an incandescent floor lamp.From your perspective, what is particularly noticeable in the changes in lighting over time?Is there something special you would like to tell us about the lighting in the Storytelling Room?
[The participants explain their roles in the handling of lighting in the building and show and tell each other about their experiences in the Storytelling Room.]The caretaker (C): I've been working in the library for almost ten years and lighting in particular has been a journey.When I started here, there were light sources and luminaires from all generations.I had to familiarize myself with which lamps fit where and make sure that everything could be stocked.Now they're being phased out and replaced by LED, and the light sources are integrated in the luminaires, so  3.
suddenly it's no longer my responsibility but the Property Office's if the lights don't work.This saves us a lot of time; we used to spend half an hour a day changing lights.Architect (A): My role in this project is that of a cultural heritage expert and I am in dialogue with the County Administrative Board about all the changes being made as the library is a listed building.The grandiose restoration plans that existed previously have, due to a lack of finances, ended up in a maintenance programme, meaning a limited renovation focusing on technical issues-among other things, the electrical system from the 1950s is worn out.Regarding the electric lighting, the building still has a unique set of original lighting fixtures, which normally disappear rather quickly, and this is of great value to the building.
Electrical consultant (EC): I have been involved in the project since those more grandiose plans; an inventory of the building's luminaires was made at that stage and now the original luminaires have been renovated.It has been important in the project to use existing mountings as much as possible.The energy issue has also been central: we expect to reduce electricity consumption by 65% by changing all lighting to LED.In here, no major changes have been made to the lighting, it basically looks the same as it did when it was installed in the 1970s.
A: What is disturbing in here today is the new emergency light, which is very bright.
Architectural historian (AH): The Storytelling Room is quite different from other rooms in the City Library.It is strongly associated with the Skandia cinema from 1923, which also informed the changes that were made here when the library was renovated 1979-81.It has become a bit of a cinema in here with recessed baffle fixtures similar to those used when Skandia was renovated in 1968.Librarian (L): I have worked with the youngest children, with songs and rhymes for babies and their parents here in the Storytelling Room.It's always fully booked and there are 12 babies and 12 adults at a time, so it gets quite full.We push the benches out of the way and sit on the floor.The parents sit with their baby in front of them and I sit in the centre.Since the babies get the light right in their eyes, we usually dim in the ceiling and keep a stronger light on me and on the mural.The bright colours of the painting attract the attention of the young children.It is fascinating to see how the children respond to the painting, from the very youngest to the older children; I think it has a lot to do with the lighting-that the painting is illuminated like this.
Lighting designer (LD): If we fantasize freely in this room, the first scene with just a floor lamp by a reading chair is a really prime example of a light zone [6] where all attention is pointing towards one direction.Then we have the second scene that you (L) describe, where the attention shifts to paintings, children, and parents.It would be interesting to experiment with different light scenes in here together with the children and study how their attention in the room changes.A library today contains many different functions with different focuses, there is no single, "right" lighting solution.There are many interesting possibilities with modern lighting; we have technical luminaires that don't glare and we can control the light for different light scenes.These are the good lighting opportunities of our time.

2 The Entrance Vestibule-Contrast and Movement
[The group gathers in the Vestibule.]DS: In older buildings, light levels are often lower and light distribution less even than in contemporary buildings.In the dark entrance vestibule, contrasts in light and colour are carefully planned to make the rotunda above appear brighter by comparison.With the strong light being situated at the back, the visitor gets used to a lower light level and is drawn up the stairs towards the light of the rotunda.[7] Is it possible to preserve contrasts between light and dark in older buildings when lighting is modernized?Is it even desirable?What requirements are in conflict with a lighting design that includes darkness?
[Two original glass light fixtures on the wall next to the large glass opening of the entrance are lit.Additional ceiling lights are temporarily switched off.We look up towards the space of the black ceiling.]1320 (2024) 012025 IOP Publishing doi:10.1088/1755-1315/1320/1/0120255 A: The dark space is suggestive; even more so when it's dark outside.
LD: The large amount of daylight and how it is reflected on the black surfaces in this room is fascinating.DS: Why do you think the luminaires are positioned next to the window at the entrance?LD: To put lamps in the windows is a Swedish tradition.The warm light of the wall lamps against the blue daylight is beautiful.It's the contrast in the colour of the light that allows you to see the warm light; if there had been a cold light in the lamps, you wouldn't have seen the light at all.DS: Look upstairs, the sun is coming into the rotunda.We're lucky!LD: When the sun comes in like this everything stops for a moment.A little bit of sunlight is so much more interesting than the light from a big glass facade.DS: Is the additional lighting in the ceiling necessary?EC: We can't meet requirements in here otherwise, not with the differences in height levels.
L: At night it's completely dark in here without the lights and there's no handrail to hold on to.This poses an accessibility issue for those with poor eyesight.I don't know if it's light-related, but we've had incidents here in the evening-an elderly man fell relatively recently.DS: But do the lights need to be on at all times, even during the day?EC: During the day, on the way in and up, it's ok, but when you go out again and are met by the strong backlight, even the contrast markings on the steps won't help, you sort of step out into the air.With the new control system I installed, each luminaire can be controlled individually so it would be possible to control the lighting against daylight sensors outside, but it has not been done.L: There are many aspects to take into account in this building: the unique architecture and the cultural heritage but also the daily use of the library from the perspective of the staff and primarily the visitors.When I give tours of the building, the group usually gathers in the vestibule, which is a good place to talk about the architectural motif of the long staircase and the democratic idea of access to books for all.But it is difficult to gather here, it is so crowded, so dark and narrow, and people pass by all the time.This entrance can actually be perceived as a barrier for inexperienced library users, the first time they visit the building.
[The conversation in the vestibule exemplifies the contradiction between the original high-contrast lighting with low light levels and today's needs and requirements for accessibility.A number of typical characteristics of older lighting design are identified through the example of the vestibule, such as lowering the light level for adaptation between inside and outside, emphasis on contrast, and a daylightbased lighting design that allows for lighting events.]

3 The Rotunda-Spatial Lighting and the Motion of Daylight
[We ascend the stairs up to the Rotunda.]DS: We will look at the space through two different lighting scenarios: one that mimics the original lighting from 1928, where only wall lamps and the large glass pendant in the centre of the room are lit; and the other representing the current lighting situation with additional uplighting and vertical light on the bookshelves.
To the original scene, we welcome a new participant, Erik Blomberg, who in a review of the library that was published in its opening year, describes how he, after negotiating "the dark and tunnel-like vestibule," experiences a sense of relief in reaching the bright, high Rotunda with its changing light, noting "in the centre of the wall, a ring of narrow windows.It is these windows, with their shifting daylight across the walls, that bring to the interior a warm and vibrant illumination, filling out the large dimensions and somewhat abstract form.[...] The removal of the dome was, from this point of view, a real gain."[8] AH: The glass dome was an early proposal that would have provided more light from above.
IOP Publishing doi:10.1088/1755-1315/1320/1/0120256 LD: I think it's great that there isn't a dome, and that the light from the windows is instead reflected on the white wall surface.DS: What do you think, is it perceived as a daylit room and if so, why?
[The group looks up at the drum, where daylight is reflected on the walls, no direct sunlight enters, and it is rather quiet.A short silence, then the conversation takes off.We talk about memories of previous light events in the rotunda, such as when the low winter sun shone straight through the room.]LD: I call these light events "magic moments".They have a very high quality and are something that I think we should try to reintroduce into architecture again.But that requires a discussion about the role of standards.Standards try to describe minimal nuisance and an acceptable level; they make light seem indifferent and flat.The ever-changing nature of daylight is an amazing quality that we should find ways to recapture; it's sustainable and it connects us to the season and the day.With all the digital tools we have today, we could easily map the "magic moments" that can happen in this building and then try to reintroduce them.The connection to daylight has become a luxury.When this building was constructed, daylight was just a light source and artificial light was expensive.Now it is the other way around and daylight has become a luxury.L: Those of us who work here are constantly busy meeting all the visitors, so I usually don't have time to think about where I am, but then suddenly something happens with the light-as you say-and I'm reminded that I'm here.I'm also often reminded by visitors what a fantastic environment this is.
AH: It strikes me that in the original scenario the books are in darkness, in the background, and become a bit like wallpaper.The dark bookshelves were a practical problem that was recognised early on.Already in the 1940s, loose luminaires were installed to direct light onto the books; these were later replaced by shelf lighting.I understand the need for light on the bookshelves, I think it is necessary.
DS: But on the other hand, the contrast with the dark bookshelves makes the drum appear brighter.AH: Yes, and it was even more apparent back then when the books were bound in uniform leather bindings in muted colours.
A: The contrast is also found in the treatment of the materials.Down here and on the way up the stairs everything is so finely chiselled compared to the drum above which has that very rough wall surface.
[C adjusts the lighting to the contemporary scene.Vertical lights on bookshelves and up-lights on the wall of the drum above the edge of the bookshelves are added.The group's intensity level rises, the participants spread out and engage in several simultaneous lively conversations about the difference between the new and old lighting.]DS: I have to ask the group to gather again.We will miss all the exciting things you're talking about otherwise.How would you describe the difference in perception of light and space between the two scenarios?AH: In the previous example, the gaze was drawn upwards to the space in the drum.Now the gaze is drawn down to the books.There's a point to that: it's the books you're after here.
A: The first scene was the classic library, a bit like a former mansion, while this scenario seems more fragmented-a bit more like "confetti," as you (AH) said.The uplights are difficult to handle I think, because it so clearly changes the experience of the room.DS: Yes, and together with the strong vertical light, I think a lot of the daylight feeling is lost.But at the same time, I understand the practical necessity, and perhaps also the symbolic value, of making the books more visible.
LD: The attention in the room shifts.We move from the room and the ceremonial, to the inviting books in all colours, a modern democratic wallpaper.
[C informs the group that the renovation has brought a clear improvement to their work.The large pendulum can now be hoisted all the way down, whereas previously a scaffold was required to reach it.Above all, the switch to LED means that there is basically no need to change light sources.]C: The worst thing was changing the fluorescent tubes for the up-light above the bookcase.Five years ago, we changed all 144 tubes on the ladder in the narrow aisle, it was a hell to change, so I am happy to avoid that!LD: I think it's important to discuss light quality now that we have LED.I felt immediately when you switched on the light on the bookshelves that it is a high-quality light.It is a light that tastes and touches.If it had been a standard LED, it would have been a completely different experience.
EC: Yes, the LEDs here have a Ra index of between 92 and 98, a great improvement compared to the previous fluorescent tubes.
[LD measures the illuminance at the shelves with a luxmeter] LD: There is a lot of light here and strangely enough it still feels good.High levels that one would be afraid of in a calculation can turn out fine when the light quality is good, but also because the lighting experience is logarithmic.This is yet another reason to discuss the standards.
[The effect of the new lighting is the subject of a lively discussion and an improvised test lighting situation arises.C leaves to switch off the uplight and the group studies the difference and the effect it has on the room.We agree that on a day like this, the room is better without the uplight.EC points out that it is different on a dark November evening, then he thinks the uplight is needed.AH adds that the uplight could be switched off during the light season.] A: What about the light on the bookshelves?Does it need to be so bright on the shelves or can it be dimmed?EC: Each shelf can be dimmed individually, but we need to have 100 lux on the lowest shelf to comply with the requirements for vertical light from the Cultural Administration.
[LD measures with the luxmeter to 2000 lux at the top and 600 lux on the bottom shelf.C takes the initiative to go and adjust the vertical lighting.]C: The pre-setting was 90% and now I have reduced it to 50%.Do you think it is better this way?Is it possible to read the backs of the books?I think the room is more pleasant and a little less "confetti," as you called it.
[Everyone in the group agrees.]EC: But the levels need to be tested on several occasions.DS: It depends on whether you (C) are still in the building and can control these things.
[Laughter.]LD: The adjustment of the light, which is one of the most important things, is rarely prioritized in projects.A number of tests are required to cover different situations.It would be interesting to try and do an evening scenario in here.When the sun shines brightly, it is experienced despite modern high light levels, but at dusk a low dimmed general lighting is required.It saves energy and it's also not healthy for people to walk around in too much light all the time.EC: The large glass pendant can be dimmed and the colour temperature adjusted from 2,700 K to 6,000 K. DS: But when would you want a cooler light in the glass pendant?EC: It was a request from the organization.You can have it yellow for Easter and red for Christmas if you want, but whether it will be used I don't know.
A: I would prefer not to use it.For some events it might be ok, but the main setting should be warm.
IOP Publishing doi:10.1088/1755-1315/1320/1/0120258 AH: I think the main point of the new installation is exactly what we are doing now.That the light can be regulated and varied for different occasions and that you can show the library as it was originally lit if you want.Before, it was very static and difficult to make any kind of changes at all.
[In the Rotunda the group visually evaluates and compares two different light scenarios.We discuss how light shifts the attention from the high room in the original scenario, to the level of the bookshelves in the contemporary scene.In the original scenario, the movement of daylight and "magical moments" are recognised as important qualities, a "luxury" that should be reintroduced in building design.In the contemporary scene, we discuss the importance of light quality and the great potential of lighting control to adapt the light to different situations and needs.]

4 South Reading Room-Light for Reading
[The group walks from the Rotunda and gathers in the South Reading Room] DS: When the library opened in 1928, the reading rooms were heavily criticized for their poor lighting.Blomberg writes in his review that the rooms "do not really come into their own because of the poor lighting.The windows are too high and too small or too few, however one wants to look at it.The reader finds himself in a region below the flow of light, sometimes almost in semi-darkness."According to Blomberg, this is because the architect let the composition of the façade determine the character of the light sources instead of the other way around."It is strange," Blomberg writes, "that the architect neglected something as fundamental in a reading room as the lighting."[8] What is important when creating good reading light in libraries today?How have the needs and conditions changed?AH: It was probably deliberate that the reading rooms should be quite dark and that you should concentrate on the book at your reading place.But there is no doubt that the light was inadequate; that has been a recurring criticism.Not only due to the fact that individual artificial light sources were relatively few and weak, but also because the walls and ceiling were covered with matte plaster in a muted tone, which meant that daylight was not reflected very much.DS: So, there was a stronger contrast in the reading rooms between reading light and a darker room and an overall contrast between the darker reading rooms around the light Rotunda in the middle?AH: Yes, and a high contrast between windows and walls.The reading rooms were painted white in 1935.
A: That the colour scheme was so short-lived was certainly due to the need for more light, but wasn't it also an architectural fashion that changed and Asplund with it?It became funkis [functionalist].The original colour scheme was typically 1920s classicism, like Thorvaldsen's Museum in Copenhagen, which was a source of inspiration at the time.
AH: It is exciting to see the change that has taken place in relation to the light source.First, there were incandescent lights everywhere in the amps and reading lamps.When the halls were painted white, the reflectors came with a kind of strong discharge lamps and all the reading lamps were cut down and the original glass amps ended up in the basement.Then in the 1940s, fluorescent tubes were added along the edges, and later the reading lamps returned in a new model.

DS [turns to the electrical consultant]: What have you changed with the lighting in here?
EC: It was a precondition that we use the existing ramp fixtures; we have replaced old fluorescent tubes with LED.After a test of the lighting, the screen above the bookshelves was developed by the architect as a way of hiding fixtures.It also serves as an installation zone, a way to get around the space without penetrating with holes.The lighting is not adjusted yet, especially not the uplights.
A: Yes, the uplights look a bit crazy; the light is sharp here and over there it's diffuse and sort of floats… [DS tries to switch off the uplight, but can't find the right button.She finally succeeds.]LD: You could feel it immediately: when the uplight was turned off, the room became more pleasant.I think it would be even more inviting if the lights at the reading place were on.They are a central part of the room.Now there is nothing that invites you to read and you should feel tempted to do so.DS: Today, the digital screens, which are light sources themselves, have partially replaced the books.L: Yes, but the reading lamps here are used extensively anyway.When I work in the evening, I have to go and switch them off one by one, manually, before the library closes.
[In the South Reading Room, we talk about how the colours and materials used in different architectural styles affect the experience of light.The rapid pace of change of electric lighting is exemplified by all the different types of lights that have been used in the reading rooms.The transition from books to digital screens is briefly discussed.Once again, we talk about how light directs attention in the room, this time exemplified by the uplights and reading lamps.]

5 West Reading Room-Shifting Ideals in Lighting and Collaboration across Disciplines
DS: The West Reading Room was built in 1932 and differs in style from the original reading rooms.At this time, Asplund wrote in the journal ERA about new lighting technology, which he described as having put "a new and effective constructive element in the hands of the architect."In the article, he emphasized the importance of a close collaboration between the architect and the electrical engineer, stating that: The rational use of light, in relation to all of its shifting applications, relies on complex techniques which in turn require a great deal of experience and specialized knowledge; it is therefore important that architects and lighting engineers collaborate closely in solving issues pertaining to lighting technology.The absence of such cooperation can lead to a great deal of laborious fumbling and tinkering, which is also costly and time-consuming, for the intended effect to be achieved.[9] Which competences are involved in the work with light in buildings today?How do different competences cooperate?DS: There are many more people involved in the lighting field today, not just the architect and the electrical engineer.EC: Yes, and then on top of that we have a lot of experts and specifications.Before, when it was just me and A, it was easy, but now we have ten more people to satisfy.
A: Yes, it can get a bit hectic.There is no established hierarchy regarding who is in charge.
LD: Lighting has become more complex: it is no longer only the architect who works with it, engineers do the calculations (one makes a projection regarding sunlight, another daylight, and the architect gets a spreadsheet back).But I'm optimistic, because young people today are so digitally skilled.We in the older generation want simple rules-we design poorly in relation to the possibilities that exist with the new digital tools.
A: I was thinking about Asplund's article.The interest in lighting doesn't exist in the architectural profession in the same way today.This is a problem that has existed for the 40 years I have been working.There are so many luminaires and no overview-you get overwhelmed.LD: Yes, there's a huge amount.But architects often look at luminaires as an object.If you draw how the light is distributed, however, there are only a certain number of luminaire types.DS: There is a requirement to preserve original luminaires in a cultural heritage building like this one, but is there also a cultural-heritage value in the effect of the light?A: Yes, I think so.DS: Asplund writes about achieving "the intended effect" of light-but what effect do we want to achieve?A: Yes, and how can we formulate it?DS: I think the daylight is experienced differently here than in the other rooms, the windows are different and the boundary between inside and outside is less apparent here.L: Yes, there is a big difference between the colour scheme in here and outside-that's something I also hear from the visitors.The other rooms are perceived as murky and darker.This room opens up when you enter it.The whole wall is covered with windows and you can actually see trees from inside here.But it gets very hot in here in the summer, and very cold in the winter.AH: So, there's a challenge here in terms of solar radiation and radiators for future renovation work.I like to emphasize this room, which is clearly different from the rest of the building.It's like a pavilion at the Stockholm Exhibition with the rounded shape of the roof and the way the light enters it.Accounts from the employees who worked on the design of this room exist, which include a discussion about how the light should enter and about the curtains, so there was obviously an awareness of the lighting.Something happens after the Stockholm Exhibition and general interest in lighting increases.Before that, I find that Asplund's view of lighting is a bit decorative, he is more interested in how the fixtures look than in the light they provide.[AH directs to DS] You have pointed out the importance of contrast in the lighting of the older parts of the building, but in here there has been a deliberate change of strategy.You get the feeling that it is the general lighting that matters here.DS: Yeah, for sure.What matters is light and air and the room doesn't have the inward-looking feeling the older parts have.AH: Yes, and in a way that makes it easier to manage.Even though there are a lot of additions of artificial light fixtures in here, they do not interfere with the overall picture.DS: That's a really good point.As soon as a light is added to a darker room, the whole lighting scheme changes.It's much more difficult to maintain the character of a darker room than in a room with a higher light level.
[AH and LS agree.][In the West Reading Room, the discussion centres on the increasing number of competences and requirements involved in working with light in buildings today.The group agrees that the architect's interest and role in lighting has shifted over time and that the responsibility for lighting design has moved from the architect to other specialists-engineers and lighting designers.]

Findings and discussion
Asplund wrote in the aforementioned article in ERA 1930, about the importance of collaboration in order to achieve the "intended effect" of light, but what effect do we want to achieve?And as A says: how can we formulate it?One possible answer to this question is demonstrated in the conversation during the seminar and through the improvised test lighting that occurred in the Rotunda.
According to Nel Janssens, a "conversation"-as opposed to knowledge production through discussion-offers a different way of making sense.[10] Conversations use questions to combine different issues and make unforeseen connections.Conversations are "syncretic" because they are about creating a new whole without removing the contradictions between the parts.[10] The description is applicable to the field of lighting where many different perspectives, even if contradictory, need to find ways to interact in order for knowledge to be utilized and developed.Janssens proposes curated conversations using "instructs" as a research tool.As a method, a qualitative conversation requires the design and curation of its material "instructs" and its immaterial instructions in order to provide a structure in which interaction can take place.[10] The walking seminar used the building as a material "instruct" that enabled a variety of experiences through the interaction between the participants, and between the participants and the material structure.
There is no instrument other than the human eye that can be used in order to describe our visual experience of light.[11] In order to develop a common language for the visual experience of light, the specific spatial context is crucial.Observing and discussing light together provides a unique opportunity to develop a common language for what we perceive, and serves as an exercise in articulating and communicating the effects of light.By putting words to what we see, we see more.[12] The fact that the spatial experience of light is situation-dependent-the interaction of light with the space, the objects, and the observer is never quite the same-does not mean that the knowledge gained from such situations cannot be utilized.By attentively and systematically conversing about aspects of light, observations and relationships can be recognised, which builds experience that can be used in new ways in future situations.
During the seminar, a recurring theme was how light directs attention in a room and how attention shifts when lighting changes.Along the walk, participants put into words some of the characteristics that were present in the original lighting design: the lower light level, the emphasis on contrasts in colour of light, and between light and darkness.The ever-changing daylight was considered an important quality and, in contemporary architecture, a luxury, that anchors us in time and season, and allows for light events -"magic moments".The conversation revealed how these characteristics can be connected to the experience of a more ceremonial architecture; the darkness in the vestibule was suggestive and, in contrast to the darkness, the light up in the rotunda appeared even brighter.As the light changed, attention shifted within the room, and consequently, the role of light was also transformed.In the original lighting scene of the Rotunda, attention was directed towards the room, the gaze was drawn upwards to the high bright space.In the contemporary scene, the attention shifted from the room to the inviting books in all colours, and an emphasis was placed on the lower part of the room where people are.
The good lighting possibilities but also the increased complexity in contemporary lighting were exemplified by the building's new control system and its complete transition to LED.The control system enables pre-set lighting scenarios for different situations: for instance, showing the light as it once was, or adapting it to the different needs of a modern library.However, the important act of setting lighting is rarely given priority in practice and the question is rarely asked: Who is responsible for operating the system?
With LED, light quality has become an important issue.The vertical lighting of the bookshelves in the Rotunda has a noticeably good quality, it tastes and touches, and suddenly a high illuminance level that would raise concern in a calculation seems surprisingly good.This observation gives rise to one of several discussions on the role of standards, their legitimacy, and the limiting role that they play in lighting design.With all the digital tools now available, could we find new ways to reintroduce the qualities of daylight, to allow dusk and potential light events to be visible?And how would that interfere with the current standards?
At our last stop, Asplund's article on the collaboration between the architect and the electrical engineer opened up a discussion on the increasing number of competences and requirements involved in lighting.We agreed that working with light has become more complex and that an interest in light does not exist within the architectural profession in the same way that it did during Asplund's time.
One of the participants mentioned the large amount of time saved per day in lighting maintenance after the transition to LED and that the demarcation of who is responsible for lighting has changed.[13] Leaving aside the hindering factors-trends and changing needs in lighting and the industry's desire to sell-what would a slowdown in the rapid pace of change of electric lighting (compared to other changes in a building) mean for lighting design?Could a slower pace of change give electric lighting a more permanent and integrated role in our buildings, where it would be less likely to be perceived as a loose technical installation?And in turn, could a more integrated approach to lighting, based on principles rather than products, revive architects' interest in light and contribute to greater collaboration between disciplines where daylight and electric light were designed together?This hypothetical scenario that would favour a more thoughtful lighting design with the potential to stand the test of time could be seen as a goal worth striving for.
The walking seminar presented in this article is part of a research project aimed at developing a method rather than solving a concrete lighting design task.The method is therefore not directly transferable to practice, but the outcome of the seminar shows the benefits of approaching the lighting task transdisciplinarily also in practice.The seminar exemplifies how new knowledge can be generated by combining different disciplines such as building history, technology, legal frameworks, spatial design, as well as practical and social aspects-new knowledge that is essential for creating long-term integrated lighting solutions.All participants expressed the view that they had gained new knowledge during the seminar, which they would take with them into future work situations.The seminar shows that the building process is in need of a planning step or "category" that could be used in practice in the initial and final stages of projects to ensure integrated lighting solutions and knowledge transfer in the field of lighting, a finding that is useful for future projects.

Conclusion
As the conversations between the seminar participants described and summarized in this paper show, the knowledge basis needed for a more informed lighting design already exists, but it is not utilized because it contains different perspectives that rarely meet.Therefore, collaboration and dialogue between different disciplines is a prerequisite for putting knowledge into practice.The outcome of the seminar shows the potential of transdisciplinary methods for dialogues to achieve this.It demonstrates how conversations based on a specific spatial situation make it possible to concretize and share the visual experience of light, and to talk about it.The question of transdisciplinary conversations may be key in all forms of architectural design practices, but in lighting it becomes especially pertinent, as lighting technology develops fast and in renovations is often not treated as an integral part of an existing building.During the transdisciplinary conversation, different perspectives on light, their contradictions, and unforeseen connections became visible, building a meaningful narrative around the many roles of light.This means that, if transdisciplinary dialogue methods are allowed to be developed and implemented in the lighting field, there are good possibilities for a more informed and spatially integrated lighting design.

Figure 1 :
Figure 1: Information sent to the participants showing the route and themes for the walking seminar