When shopping for a light bulb or reading about good light, you've probably come across the terms lumens and lux. They sound similar, but they describe two very different things. Understanding the difference is essential, especially when it comes to lighting for health and wellbeing. Jan Sleepman What are lumens? Lumens (lm) measure the total amount of light a lamp produces. Think of lumens as the light output of the source itself. The higher the lumen value, the more light the lamp emits in all directions. However, lumens don't tell you how much light actually reaches you. What is lux? Lux (lx) measures how much light, or how many lumen, falls on a surface. For the health aspects of light, that surface is usually your eyes. One lux equals one lumen spread over one square metre. This means lux depends not only on the lamp's output but also on factors such as, the distance from the light source and the direction of the light. In other words, lux tells you how much light is actually available where you are. Why lux matters more for health For your biological clock, it doesn't matter how many lumens a lamp produces; it matters how much light reaches your eyes. Imagine sitting beneath a very bright lamp. If the lamp is high above you or poorly directed, only a limited amount of light may actually reach your eyes. Conversely, sitting close to a window on an overcast day may expose you to thousands of lux, even though the sky doesn't appear particularly bright. This is why chronobiologists and lighting professionals often talk about lux at eye level, rather than the lumen rating printed on the packaging. A practical example Imagine you buy a lamp that produces 2,000 lumens.If the light is spread across a large room, the illumination at your desk might only be 200 lux. Move the same lamp closer or focus the light more effectively, and your desk could receive 500 lux or more. The lamp hasn't changed; only the amount of light reaching the surface has.

During the Guangzhou International Lighting Exhibition (GILE 2026) , deLIGHTed Talks Asia brought together an exceptional group of scientists, clinicians, lighting designers, architects, manufacturers, building professionals and industry leaders. Their backgrounds differed, but they shared one ambition: to accelerate the transition from conventional lighting to Good Light that genuinely improves people's lives. The central question throughout the event was straightforward: How can Good Light move from promising concepts to measurable, verifiable and scalable solutions? Across keynote presentations, panel discussions and Focus Group sessions, speakers explored topics ranging from circadian science and brain function to healthcare, senior living, healthy homes, integrative lighting, lighting design, building performance and owner value. Although the subjects varied, a common theme emerged. The lighting industry has reached a new stage in its development. Technical innovation alone is no longer enough. Future value will increasingly be created by improving sleep, wellbeing, health and the overall human experience inside buildings. That transition also requires a different way of working. Good Light cannot be built on marketing claims alone. It requires scientific evidence, thoughtful design, practical implementation and objective verification. It calls for collaboration between science, medicine, lighting design, manufacturers, building owners and standards organisations. Only then can Good Light become a trusted and widely adopted part of healthy buildings. The discussions during deLIGHTed Talks Asia demonstrated that this transition is already underway. Across disciplines there is growing agreement that lighting should no longer be evaluated only by energy use, efficiency or visual performance, but also by the value it creates for people and for society. The programme featured presentations by leading international experts, including: Robert Lucas: Measuring and Manipulating Light to Support Healthy Rhythms Marijke Gordijn: Good Light, Rhythms, and Circadian Health Jan Denneman: A Wake-Up Call — From Illumination to Human Outcomes Kei Haraguchi / Nichia: Dynasolis™ — Moving Beyond LPW to Create New Value Anne Berends: SunLED Life Science: Near-Infrared Light and Wellbeing Jeff Miller: Beyond Aesthetics — How Designers Translate Science into Human Experience Kevan Shaw: Practical Aspects for Implementing Integrative Lighting Martin Klaasen / VLDC: Future Forum Debrief — Trends, Opportunities and Recommendations for Life Centric Lighting Amardeep Dugar: Lighting Design for Wellness — A Salutogenic Framework Oliver Stefani: Evening Light, Sleep, and Family Wellbeing Zhao Hongyi: Light in Healthcare — From Compliance Lighting to Clinical Environment Design Professor Yandan Lin: Healthy Homes — The Next Upgrade Beyond Smart and Aesthetic Lighting Zheng Hongcheng: No Verification, No True Healthy Light — A Scientific Interpretation Based on EEG Dr. Wei-Jye Lin: How Light Acts on the Brain — From Visual Circuits and Brain Clearance to Verifiable Application Value IWBI / WELL Perspective / Richard Wei-Shun Chang: From Wellness Story to Asset Value Together, these presentations illustrate how rapidly the field is evolving and how Good Light is becoming a multidisciplinary movement. The challenge now is no longer understanding why Good Light matters, but how to implement it responsibly, verify its impact and deliver measurable value for people, buildings and society.

The Good Light Group is pleased to welcome Kevan Shaw as an advisor. Kevan is an internationally respected lighting designer with more than 40 years of experience in architectural, museum and urban lighting, and currently serves as a Director of the International Association of Lighting Designers (IALD). Sunset in Iceland Kevan will strengthen our work particularly in the field of lighting design, helping to further integrate health and wellbeing into design practice. His extensive international network, close ties with the IALD, and experience in developing industry guidance and white papers will be invaluable as we expand our practical recommendations on integrative lighting design. We are delighted that Kevan is joining our growing team of advisors and look forward to working together to help make good light an integral part of healthier buildings and healthier lives. Kevan Shaw

Daylight saving time gives us longer, brighter evenings, but it can also disrupt our natural body clock. Even weeks after the clocks change, many people still feel more tired, find it harder to fall asleep, or struggle to wake up in the morning. The reason is simple. Our body clock is primarily regulated by light. When the clocks move forward by one hour, our social schedule changes overnight, but our body clock does not. It needs time and the right light signals to adjust. Photo by Solving Healthcare on Unsplash One of the best ways to adapt is to get plenty of light in the morning. Morning light is the strongest signal that tells your body the day has started. Try to get outside as soon as possible after waking up. A short walk, breakfast on the terrace, or cycling to work can make a significant difference. Research suggests that most adults need at least 500 lux at eye level during the day to support alertness and help regulate their body clock. Outdoor daylight easily exceeds this level, even on a cloudy day. If spending time outdoors is not possible, sit close to a window or use bright, high-quality electric lighting to reach approximately 500 lux at eye level during the first part of the day. The challenge with daylight saving time is that your body may still be running on the old schedule. If you normally go to bed at 22:00hr, your body may feel as though it is only 21:00hr. As a result, you may not feel sleepy when you want to go to bed. Late evening daylight can make this adjustment even more difficult. Bright light in the evening tells your body that it is still daytime. This delays your body clock and slows down the natural processes that prepare you for sleep. The result can be difficulty falling asleep, poorer sleep quality, and increased tiredness the next day. To help your body prepare for sleep, keep the three hours before bedtime as dim as possible. Close curtains or blinds, dim indoor lighting, avoid bright screens, and switch your devices to night mode. Ideally, keep light levels below 10 lux at eye level during the last few hours before bed. A darker evening environment allows your body to produce melatonin naturally and prepare for a restorative night's sleep. Most people adapt to daylight saving time within a few weeks. You can speed up this process by following a simple rule: get as much light as possible in the morning and as little light as possible in the evening. Daylight saving time changes the clock. Good light helps your body catch up. The right light at the right time supports better sleep, more energy, a better mood, and a healthier life.

A summary of the article by Jan Denneman and Dave Hollingsbee, published in Arc, a magazine for architects and interior designers. For years, the lighting industry has focused on three key goals: functionality, design, and sustainability. We have made remarkable progress in energy efficiency, circular manufacturing, and smarter lighting controls. But there is a fourth dimension that deserves equal attention: sleep, human health and performance. Photo by copernico on Unsplash One of the most compelling arguments comes from the “3-30-300 rule,” which highlights how organisations typically spend around €3 on utilities, €30 on space, and €300 on people for every square foot of building space. While lighting is often evaluated based on energy savings, the greatest financial impact may come from its influence on employees. Even a 1% improvement in productivity or reduction in absenteeism can save hundreds of thousands of euros annually, far exceeding typical lighting energy costs. Recent discoveries in chronobiology support this perspective. Researchers have shown that light does much more than enable vision; it regulates our internal body clock, sleep quality, alertness, and overall health. Modern indoor lifestyles often expose us to too little daylight during the day and too much artificial light in the evening, disrupting natural circadian rhythms. The result can be poorer sleep, reduced concentration, and lower workplace performance. We introduced the concept of a “light diet,” comparing light exposure to nutrition. Just as a healthy diet supports physical wellbeing, the quality, intensity, and timing of light exposure play a critical role in human health. This means lighting should no longer be considered background infrastructure, but an active contributor to wellbeing and productivity. We advocate for greater access to natural daylight, and for electric lighting that compensates the lack of natural daylight. We want to encourages architects, designers, developers, and policymakers to move beyond compliance and energy metrics and instead focus on measurable human outcomes. Ultimately, the message is clear: sustainability is not only about reducing energy consumption. Truly sustainable buildings must also support the health, resilience, and performance of the people who use them. The challenge facing the industry is no longer whether healthier lighting is possible, it is about entering this new chapter of the lighting industry. Read the full article here

We’ve organised our 25th Good Light Group meeting. The topics included: Jan Denneman with the Good Light Group news. Lawrence Lin presents an update on the Good Light Group Asia & more info about the deLIGHTed Talks Asia. Maarten Voorhuis shares his insights into the use of the light-measuring function on the Apple Watch. Photo by Jonatas Daniel on Unsplash Missed the Good Light Group Meeting? Watch the presentions online here: Jan Denneman - Good Light Group news Lawrence Lin - Good Light Group Asia Maarten Voorhuis - the light-measuring function on the Apple Watch Lawrence Lin - deLIGHTed Talks Asia

An epidemiological study (Stevenson et al., 2024) with participants from the UK found that people who had more ultraviolet, or UV, light exposure tended to live longer compared to people with less UV exposure. That finding might sound strange, because exposure to UV light – which is part of sunlight – is commonly communicated as a health risk factor. In fact, too much UV exposure can increase the risk of skin cancer. These new findings, however, suggest a more nuanced relationship between UV light and health, especially in cloudy, low-sunlight countries like the UK. Photo by Elizeu Dias on Unsplash The findings are based on data of 395,086 people from the UK Biobank study. For their study, the researchers quantified UV exposure from two proxies: (i) behaviour in terms of visits to solariums or sunbeds, and (ii) meteorological data of sunlight reaching the participants’ residential area. These data in turn were analysed with respect to the prevalence of deaths from heart disease, cancer, and other causes. The main finding was that people with higher UV exposure had a lower risk of dying overall, including a lower risks of dying from cardiovascular disease and cancer. Solarium users had about a 15% lower risk of death overall compared with non-users, and people living in sunnier parts of the UK also had lower death rates. In their publication, the authors discuss the mediating role of vitamin D, which is produced by the skin when exposed to UV-B light. An additional possibility discussed is UV-A light, which may help release nitric oxide in the skin. Nitric oxide, in turn, is suggested to relax blood vessels, lower blood pressure, and thereby support heart health. Importantly, these results do not mean tanning endlessly is a good idea. The researchers mention that higher UV exposure could be linked to more melanoma cases. Hence, the take-home message is not “go and bake in the sun.” Rather, it means that overly strict avoidance of sunlight might carry negative rebound effects for health, which should be considered in the communication of health risks associated the UV – sunlight – exposure. Since public health advice often focuses on the dangers of UV exposure, a more nuanced view might be warranted. Place of residence should be considered, as these findings from a UK cohort show, since countries like the UK, are limited in sunlight exposure with an increased prevalence of low vitamin D. Based on research from the UK Biobank cohort study: Stevenson, A. C., Clemens, T., Pairo-Castineira, E., Webb, D. J., Weller, R. B., & Dibben, C. (2024). Higher ultraviolet light exposure is associated with lower mortality: An analysis of data from the UK biobank cohort study. Health and Place, 89. https://doi.org/10.1016/j.healthplace.2024.103328

We are delighted to welcome ClearLight as a new participant in our Group. At ClearLight, they believe that the way we approach lighting is fundamentally flawed. For decades, lighting has been designed around standards, efficiency, and cost reduction, while the human perspective has largely been overlooked. Good lighting, however, does far more than simply illuminate a space. It affects our biology, our natural rhythms, and our overall wellbeing. It influences how we feel, how we perform, and how we recover. “In the Good Light Group, we have found like-minded professionals who share this belief. Together, we are working towards a necessary paradigm shift: from lighting designed for standards and energy efficiency to lighting designed for people,” says Maurijn, co-founder of ClearLight. More info about ClearLight

Light is more than something you see. When it enters your eyes, it reaches parts of your brain that regulate your sleep, your mood, your alertness, and your long-term health. This happens every time you step outside, sit under a lamp, or look at a screen, whether you notice it or not. And the pattern of light you live in, bright or dim, day or night, shapes how well your body works. How light shapes your body clock Every cell in your body follows a roughly 24-hour rhythm. This internal clock controls when you feel sleepy, when you feel awake, when hormones are released, and when your body temperature rises and falls. For the clock to work properly, it needs to stay aligned with the world outside. Light is the main signal that keeps it on track. Specialised cells at the back of your eye detect light and send signals to the brain regions that run this clock. This happens whether you notice the light or not. Bright light in the morning tells your body it is daytime: you wake up properly, you feel alert, and your clock gets set for the day ahead. Low light in the evening and darkness at night tell your body it is time to wind down, release the sleep hormone melatonin, and rest. The problem is that modern life flips this pattern. Most of us spend our days indoors, where light levels are far too low to give the body a strong daytime signal. In the evening, we surround ourselves with bright indoor lighting and screens, which the body reads as continued daylight. Days are too dim, nights are too bright, and the internal clock drifts out of sync. When that happens, sleep gets worse. Mood and alertness suffer. Over time, the mismatch can affect physical health too. The good news is that light exposure is something you can adjust. You do not need supplements or special products. A few simple behavioural changes are enough to give your body the light signals it expects. Five practical tips Get outside in the morning Even on a cloudy winter day, outdoor light is far brighter than a typical indoor environment. Spending time outside, especially in the morning, is the most reliable way to give your body the light signal it needs. Standard office lighting is usually not enough on its own. Sitting near a window helps, but going outside is better. Sit near a window when you are indoors Most of us cannot spend the whole day outside. Where you sit indoors makes a real difference. Natural light through a window is still much brighter than most artificial lighting, and the closer you are to the window, the more light reaches your eyes. Position your desk or your usual seat to face a window if you can. Dim your lights two to three hours before bed Bright light in the evening tells your body it is still daytime. It delays your internal clock and suppresses melatonin, which makes it harder to fall asleep. Dim your overhead lights, switch to lower lamps, and avoid bright bathroom lights right before bed. The contrast between a bright day and a dim evening is what your body is looking for. Keep screens dim in the evening Phones, tablets, and laptops are bright. The simplest thing you can do is turn the brightness down. Reducing screen brightness matters more than switching to a warmer colour setting. Better still, put screens away in the hour before sleep and let the room around you be dim. Sleep in darkness Even low light levels during sleep can affect sleep quality and the timing of your body clock. Use blackout curtains if outside light reaches your bedroom. Cover or remove glowing electronics. If you need a light during the night, keep it as dim as possible. So light is a powerful signal for your body. Bright days, dim evenings, and dark nights are what your biology expects. Getting that pattern right supports your sleep, your mood, and your long-term health, and the most effective steps are behavioural and free.

Jeroen Bosch Hospital (JBZ) in Den Bosch, the Netherlands, has reported encouraging early results from a new night-shift system called a “chrono-schedule”. In a pilot study, nurses working under the new system said they felt less exhausted after night shifts, had less difficulty staying awake, and recovered more quickly afterwards. Photo by Amir Arabshahi on Unsplash Instead of working a full night shift, staff worked shorter shifts from 8.00 pm to 4.00 am or from 4.00 am to 12.00 pm, with a daytime shift in between. This meant they could still sleep during part of the night. The trial also found fewer stomach and bowel complaints, and many nurses said they felt recovered within a day rather than needing two or three days. Doctors involved in the project say the new system appears to fit better with the body’s natural rhythm. However, it may not suit everyone, as it can affect social life and evening activities. Because some of the staff do not want to go back to the old schedule, the hospital will continue using the chrono-schedule for now and will carry out a follow-up study in the summer before deciding whether to introduce it permanently.

Sleep is fundamental to our health, performance, and wellbeing — yet it is increasingly disrupted by our everyday’s actions and the way we design and light our buildings. This CIBSE-approved CPD course explores the science of sleep, our internal body clock, and how integrative lighting design can actively support healthier sleep–wake rhythms. Photo by Gregory Pappas on unsplash Understanding sleep: more than just “switching off” A clear overview of what sleep actually is, breaking it down into its main stages: Stage 1 – Drowsy sleep (5–10 minutes):The transition between wakefulness and sleep. Muscle relaxation begins, eyes roll slowly, and we remain sensitive to surrounding noise. Stage 2 – Light sleep (10–25 minutes):Brain activity and heart rate slow, body temperature drops, and we can still be woken easily. Stage 3 – Deep sleep (20–40 minutes):The most restorative phase of sleep. We become largely insensitive to noise, slow brain waves dominate, and the body focuses on physical recovery, tissue repair, and growth hormone release. REM sleep – Paradoxical sleep (20–40 minutes):Characterised by rapid eye movements, vivid dreaming, and muscle relaxation. This stage plays a critical role in memory consolidation and emotional processing. Understanding these stages, how they are organised in stages and their connections helps explain why both sleep quantity and quality are vital for health.   Our internal clock and the role of light A key part of the course focuses on the body’s internal clock, or circadian rhythm. This clock is primarily synchronised by the external 24-hour light–dark cycle, known as a photic zeitgeber. Daylight entering the eyes sends signals to the brain’s master clock — the suprachiasmatic nucleus (SCN) — which regulates bodily functions and hormone production throughout the day. In addition, non-photic zeitgebers such as sleep routines, physical activity, social interaction, and meal timing also influence our rhythms via peripheral oscillators.   Why indoor lighting often works against us Modern indoor environments frequently provide lighting that is too dim during the day and too bright in the evening. This mismatch can undermine circadian entrainment, disrupt sleep quality, and negatively affect health and alertness. The course introduces melanopic equivalent daylight illuminance (m-EDI lux) — a metric that quantifies how light affects the melanopsin system in the eye, which is crucial for circadian regulation.   What “good light” looks like Based on current research, the course outlines practical m-EDI* targets: Daytime: Minimum 250 m-EDI lux (vertical) to support alertness and circadian entrainment Evening (starting at least three hours before bedtime): Maximum 10 m-EDI lux (vertical) to allow the body to prepare for sleep Sleep environment: As dark as possible, with a maximum of 1 m-EDI lux (vertical) *The m-EDI lux unit is defined in the CPD course .   Integrative lighting design in practice The CPD course introduces Integrative Lighting Design, which considers both: Visual needs (seeing and task performance) Non-visual effects (circadian regulation, sleep, and wellbeing) Through a structured design process and a real-world case study, the course demonstrates how lighting solutions can successfully support both visual comfort and biological needs.   Key takeaways By the end of the course, participants will understand that: Sleep is crucial for long-term health and wellbeing Light does far more than enable vision — it regulates our internal clock Poor indoor lighting can disrupt sleep and circadian rhythms, and affect our health Integrative lighting design can support both visual and circadian needs Well-designed projects show this approach is achievable in practice This CPD provides valuable insight for anyone involved in building design, lighting, or occupant wellbeing — offering practical knowledge to help create healthier indoor environments through better lighting.   Follow the CPD course here , a certificate is available if needed for your professional institution, after completing some questions on the course material.

Sleep doesn’t start when your head hits the pillow, it begins hours earlier with the signals you send your brain. One of the most important signals is light. To support deep, restful sleep, it’s recommended to keep light levels below 10 lux starting three hours before bedtime. Photo by Giorgio Trovato on Unsplash   How Light Affects Your Sleep Your brain uses light to decide whether it’s time to be awake or asleep. Bright light in the evening, especially artificial lighting and screens, can delay the release of hormones that helps you fall asleep. Even moderate indoor lighting can confuse your brain clock and make it harder to wind down. Keeping light levels very low in the evening tells your body that night has arrived.   Dim the Lights As bedtime approaches, gradually reduce the brightness in your home. Use: Dimmable lights Low-watt, warm-coloured lamps Indirect lighting instead of overhead lights The goal is a soft, calm environment that allows your eyes to relax.   Close the Curtains Outdoor light, from streetlights, cars, or buildings, can easily push light levels above what your brain considers “night.” Closing curtains or blinds helps block unwanted light and creates a darker, more sleep-friendly space.   Avoid Bright Screens Phones, tablets, TVs, and laptops emit light that strongly signals “daytime” to your brain. In the final three hours before bed: Avoid unnecessary screen use Lower screen brightness as much as possible Choose non-screen activities like reading Set your screen devices to night mode   Create a gentle transition to sleep By keeping light levels below 10 lux for the three hours before bedtime, your brain is going to helping you fall asleep faster and sleep more deeply.