Harmonizing Light Dosimetry: Illuminating a Unified Path
Henrik Clausen is Director of the Fagerhult Lighting Academy, as well as Associate Professor at Aalborg University in Copenhagen. He is tasked with keeping Fagerhult’s general lighting knowledge up to date, and that includes reading many scientific papers.
Sharing his thoughts on papers he finds especially interesting and/or thought-provoking is one of the aspects of this role he loves.
Recently, Henrik posed the question - ‘Can we dose the right amount of light?’
To a certain degree, we can. But, there is an underlying concern about light dosimetry, and here, Henrik would love to give you a little more to think about...
In the vast canvas of scientific exploration, the study of light's effects is like an artist's palette of endless colours. Just as different artists apply unique brushstrokes to create their masterpieces, researchers approach light dosimetry with their own methods and metrics.
These variations, while showcasing the diversity of scientific exploration, also raise a challenge — a challenge to compare and align different works of art or in this case scientific results, for a clearer, unified understanding.
Consider this: scientists from various corners of the world, armed with their tools and knowledge, delve into the realm of light dosimetry. They strive to capture the intricacies of light's influence on our well-being, just like artists capture the essence of light in their paintings. And, just as each artist's style brings forth a different story, each scientist's approach to dosimetry has the potential to yield unique insights.
These diverse approaches are like different colours on the canvas, representing the nuances of light's impact. But, imagine trying to create a cohesive artwork by blending those colours without a shared understanding of their shades and tones.
Similarly, without a common framework for measuring and quantifying light's visual, emotional, and biological effects, scientists find themselves facing a complex puzzle - how to compare their findings in a meaningful, standardised and comparable way?
It's as if a symphony is being played, with each musician interpreting the notes in their own, slightly different way. Yet, to create harmony, the musicians must follow a conductor's guidance and stay in tune with each other. Similarly, the field of light dosimetry needs a conductor - a common frame of reference that guides scientists in choosing the right "notes" (metrics and procedures) to measure light's impact consistently across studies conducted on different locations in time and space.
Imagine a world where different dosimetry studies are like puzzle pieces that fit together seamlessly. By aligning their metrics, scientists can create a clearer picture of how light affects us. This alignment doesn't have to be stifling creativity; rather, it's about providing a shared language that allows scientists to communicate their findings, methods and procedures effectively to their peers, for them to understand, compare and reproduce these findings, fostering a deeper mutual understanding and thereby the very understanding of light's biological and non-visual role in all our lives.
In this quest for alignment, researchers aim to bridge the gap between various brushstrokes of scientific exploration. By using common metrics and methods, they can enhance the comparability of their work. This, in turn, leads to a broader perspective on the effects of light, helping us understand the dosage of light we need for optimal health and well-being.
Just as artists contribute to a collective understanding of the world through their creations, scientists too, contribute to our understanding of light's impact through their studies. By harmonising their efforts, they create a symphony of knowledge that benefits us all.
So, as the world of light dosimetry continues to evolve, scientists work towards aligning their brushstrokes of discovery, painting a clearer, more harmonious picture of the profound effects of light on our lives.
Light and people
Light has always been a prerequisite for human existence. Inspired by daylight and the latest science, we can create lighting that makes life even better. Humans are made to be outdoors, and daylight affects the way we are – biologically and psychologically. New research has shed light on these links.
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Beyond What We See – Exploring the Biological Role of Light
For most of human history, people lived almost entirely under natural daylight. The rhythms of sunrise and sunset shaped sleeping patterns, activity levels and the way the body responded to the environment. Today, modern life looks very different. Humans now spend 90% of their time indoors, surrounded by artificial light and increasingly separated from the full spectrum of daylight under which humans evolved. In conversations around wellbeing and the health of the human body, some researchers are beginning to ask whether light may influence the body in ways that extend beyond vision alone. One of those researchers is neuroscientist Professor Glen Jeffery at UCL’s Institute of Ophthalmology, whose research explores the relationship between light, mitochondria, ageing and visual function, including the potential biological role of longer wavelengths beyond the visible spectrum. This interview explores his research, insights, and the growing conversation about how modern indoor environments may be changing humanity’s relationship with light - not just visually, but biologically as well. The Evolution of Humans Under Daylight At the centre of Glen’s thinking is a relatively simple idea: the human body evolved under the full spectrum of sunlight over millions of years. “So many parts of your body and systems in your body were set over exposure to sunlight over millions of years,” he explains. “Your body has lost contact with your evolutionary history.” He explains that this evolutionary perspective is central to understanding why light may matter biologically. Human physiology developed in outdoor environments where daylight exposure was continuous, dynamic and spectrally rich. Modern indoor life, by comparison, represents a dramatic environmental shift. This does not mean modern lighting is inherently harmful, but rather society may only now be beginning to understand how profoundly modern environments have changed the way humans experience light. Beyond the Visible Spectrum When it comes to designing light, conversations often focus on what people can see: brightness, colour temperature, contrast, glare and visual comfort. Glen’s research, however, explores the possibility that wavelengths outside visible vision may also influence the body. “You only see a minute amount of the spectrum of sunlight, between roughly 400 nanometres (nm) to 700nm,” he explains. Visible light occupies only a relatively narrow band within the wider electromagnetic spectrum. Beyond it sit ultraviolet wavelengths on one side and infrared wavelengths on the other - both largely invisible to the human eye. Much of his recent work has focused on longer infrared wavelengths and their potential relationship with mitochondria - the structures within cells responsible for energy production. He argues that much of the sunlight exists beyond the visible spectrum that humans experience with the naked eye. This is where the conversation begins to move beyond traditional lighting discussions and into broader biological territory. Mitochondria, Energy and Ageing A significant portion of his recent work has explored how longer wavelengths of light - particularly around 670nm and near-infrared ranges - may influence mitochondrial performance and age-related decline in both animals and humans. A term many people may be unfamiliar with, but one that plays a fundamental role in the human body, is mitochondria. Often described as the body’s energy systems, mitochondria are essential to almost every biological process. “Everything you’re doing is relying on mitochondria,” Glen says. “Whether that’s using your muscles to kick your legs out of bed, or reach out for that cup of coffee.” In simple terms, mitochondria produce ATP, the molecule that powers cellular activity. His research explores how longer-wavelength light beyond 700nm may influence the efficiency of this process. “Long wavelength light lubricates each point where there’s a slight bit of resistance,” he explains, describing how photons may help support electron transfer within cellular energy pathways. While much of the science remains under investigation, Glen believes mitochondria may sit at the centre of broader questions around ageing, metabolism and human health. “The theory that sticks to the wall hardest is called the mitochondrial theory of ageing,” he says - the idea that ageing is closely linked to the gradual decline of mitochondria over time. As mitochondria become less efficient, the body’s ability to produce energy and maintain healthy function may also deteriorate. It is, however, important not to overstate conclusions. He emphasises that this is an evolving field with many unanswered questions, and believes the relationship between light, biology and human health deserves greater attention than it currently receives. Modern Indoor Life Whilst humans evolved under natural daylight, modern life is very different. People now spend much more time indoors than previous generations, fundamentally changing daily exposure to natural light. He points not only to artificial lighting, but to indoor lifestyles more broadly. Modern life increasingly takes place inside controlled environments, often with limited exposure to the full spectrum of daylight under which humans historically evolved. “We are making ourselves vulnerable because we’re living inside,” he says, “and we’re exacerbating that vulnerability with LED lighting.” Importantly, Glen does not separate modern indoor living from lighting technology itself. Instead, he sees them as interconnected parts of a much wider environmental shift. Beyond Circadian Lighting? Over the past decade, the lighting industry has increasingly explored circadian rhythms and human-centric lighting - particularly the role of light timing and blue wavelengths in regulating sleep and alertness. Glen does not see his research as contradicting that work, but rather broadening the conversation. In his opinion, it would be a mistake to think that light only does one thing. While circadian research largely focuses on visible wavelengths associated with the body clock, Glen’s work looks further into the infrared end of the spectrum and its potential biological effects. “These are two things that run hand in hand,” he explains. For him, the growing interest in circadian lighting reflects a wider shift towards understanding that light may influence people in multiple ways beyond visibility alone. A Conversation Still Emerging Glen believes researchers may now be approaching an important moment - not because all the answers exist, but because the questions themselves are beginning to change. For decades, conversations around light have understandably focused on visibility and visual performance. Increasingly, however, researchers are exploring whether light may also influence the body in broader biological ways that remain only partially understood. Exactly where this research may lead remains uncertain. But discussions around daylight, wavelength, and human biology are beginning to open new conversations about the relationship between people, light, and the environments they spend most of their lives in. In Part 2, we explore what these emerging ideas could potentially mean for lighting design, architecture and the future of healthy indoor environments.
Celebrating Retail Design: Inside Fagerhult's Health & Beauty Retail Safari
In retail, there is still no substitute for experiencing stores in person. That idea sits at the heart of Fagerhult's Retail Safari programme. Hosted by retail consultant Phil D'Souza, the initiative brings together retailers, designers and industry specialists to explore standout store environments, share perspectives and celebrate the creativity shaping the sector. With more than 30 years of experience spanning visual merchandising, store design, retail format development and customer experience, Phil has spent much of his career exploring how physical environments influence customer behaviour, brand perception and commercial success. Today, through his consultancy work and collaboration with Fagerhult, he helps retailers create spaces that engage, inspire and perform, making him an ideal guide for these immersive retail explorations. The recent Health & Beauty Retail Safari saw participants spend an afternoon visiting 12 stores across London's West End. Rather than critiquing brands against a checklist, the safari created space for observation, discussion and inspiration, examining how retailers use layout, materials, merchandising and lighting to shape customer experiences. Qoute Different Brands, Different Answers Health and beauty proved a particularly interesting sector to explore because of the diversity of brands operating within it. "It's a really dynamic sector," says Phil. "You've got legacy brands alongside direct-to-consumer startups that have successfully transitioned into physical retail. That creates a really diverse environment." For the retailers and designers attending, that diversity was evident throughout the safari. Across the stores, participants encountered very different approaches to customer experience, despite many brands ultimately selling similar categories of products. By focusing on a single sector, the group could compare how brands interpreted space, atmosphere and product presentation in distinct ways. "You're able to look at what could ostensibly be a similar product type being presented through very different combinations of design, layout, materials and architecture," says Phil. "Ultimately, that respects the brand and creates a more immersive experience for the consumer." The Power of Product Presentation One of the standout examples came from Molton Brown's Regent Street flagship. The store uses ambient lighting to create a warm and welcoming atmosphere, with lighting also integrated directly into the shelving displays. "The thing about Molton Brown is that most bottles are clear, so customers often recognise and select products by colour," explains Phil. "What they've done by adding lighting into the shelving is almost illuminate the product from within." Unlike many brands where colour sits on the packaging, Molton Brown's clear bottles showcase the product itself. The distinctive colours of the shower gels, hand washes and bath products become a visual shorthand for different fragrances and collections, helping customers quickly spot familiar favourites or explore new options. The effect transforms the presentation of the products, amplifying the intensity of colour and helping customers navigate the range intuitively. "It almost creates this ethereal glow," he says. "They've not only lit the space, they've exploited the intensity of the colour of the product itself." For participants, it demonstrated how lighting can become part of the product experience rather than simply illuminating it. Creating Atmosphere Through Design Another memorable stop was Penhaligon's on Regent Street. For Phil, the store illustrated how lighting works most effectively when considered alongside every other element of the environment. "Penhaligon's felt like walking into someone's wonderful home," he says. Artwork, warm timber finishes, brass detailing, rich colours and discreet lighting combined to create a calm and highly immersive experience. "You suddenly realise that when you add all these things together and light them correctly, you feel very calm and very immersed in the environment," says Phil. "That's the power of good retail design underpinned by fantastic lighting solutions." Rather than drawing attention to individual features, the design worked as a cohesive whole to reinforce the brand's identity. One Brand, Two Very Different Stores One of the most interesting discussions emerged from comparing two stores operated by the same retailer. Participants visited two Aesop locations situated only a short distance apart: one on Regent Street and another on Beak Street. Despite sharing the same brand, the stores felt entirely different. The Regent Street location reflected the scale and character of its flagship surroundings, while the Beak Street store adopted a much simpler aesthetic more suited to its local context. "What was really interesting was that the store design on Beak Street reflected Beak Street, and the store design on Regent Street reflected Regent Street," says Phil. This approach extended across the brand's wider portfolio. "If you go to Kensington it's completely different again. If you go to Islington it's different again." For participants, it highlighted an increasingly sophisticated approach to retail design, where consistency comes from brand values and customer experience rather than identical store formats. "They're thinking about who's visiting the store," says Phil. "It doesn't really matter that every store isn't exactly the same. They reflect the consumer who's shopping in that location." Looking Beyond the Store Interior While much of the discussion focused on interiors, Phil encouraged participants to consider the customer experience before entering the store. "Standing outside a store is as important as being inside it," he says. Storefronts, windows and exterior lighting all play a role in shaping expectations and attracting attention within a competitive retail environment. "It's what you spot when you're walking past," he explains. "The better the environment is, the more likely you are as a consumer to consider that space." For retailers and designers alike, it served as a reminder that customer experience begins long before a purchase decision is made. Celebrating Great Retail A consistent theme throughout the safari was the desire to celebrate great retail design rather than critique it. That sense of celebration extended into the stores themselves. Ahead of the safari, the Fagerhult team spoke with the retailers they planned to visit. Phil says the response was overwhelmingly positive. “Pretty much every store said, ‘This is fantastic. Thank you so much. Yes, please come in,’’ he recalls. For him, that reaction reflected something important about physical retail: when a store has been carefully designed and invested in, teams are often proud to share it. Their enthusiasm adds another layer to the experience, reinforcing the relationship between brand, environment and people. Across the twelve stores, participants encountered a variety of approaches to lighting, layout, product presentation and customer engagement. While no two environments were the same, each demonstrated how considered design can shape the way customers experience a brand. "When you see some really good retail design, it creates fantastic ideation and fantastic creativity," adds Phil. Explore how Fagerhult can support your next retail project — from store openings to refurbishments — by getting in touch with our team. Coming soon: In a forthcoming profile feature, Phil D'Souza shares insights from more than 30 years in retail, exploring how store design, visual merchandising, customer experience and lighting have evolved, and what today's retailers can learn from creating environments that engage, inspire and perform.