Until recently, the lighting industry focused primarily on the visual function of light – that is, how well we see and how a space is illuminated from the perspective of architecture, energy efficiency, and visual comfort. Gradually, however, a more comprehensive approach to light is emerging, one that considers its non-visual (Non-Image Forming, NIF) biological effects, which have a significant impact on our health, cognitive functions, and overall well-being. This approach now resonates even among top global lighting designers affiliated with the International Association of Lighting Designers (IALD), who, in their new official document, join the recommendations of the International Commission on Illumination (CIE) and emphasize the need to see light as a key factor influencing overall human functioning.
Non-visual effects of light as part of a global design approach
Properly designed lighting should support not only visual but also emotional and physiological aspects of the human body. This means stimulating alertness, enhancing performance, and contributing to the regulation of neuroendocrine, physiological, and cognitive functions. A lack of quality light during the day can lead to increased fatigue, impaired working memory, greater susceptibility to mood swings, and reduced adaptability. Natural daylight therefore plays a vital role and is almost irreplaceable in supporting our circadian rhythms. These rhythms regulate internal biological processes, and their synchronization is key to health and quality sleep. However, we don’t always work in conditions with sufficient daylight, and this is where the expertise of architects and designers from IALD comes in – highlighting which qualities of artificial light to focus on.
Which light properties affect our health
Circadian rhythms are influenced by the amount of light (illuminance), its spectral power distribution (SPD), timing and duration of exposure, spatial distribution of light, and a person’s so-called light history. All these requirements must be considered when designing interior lighting. Current lighting rarely reaches intensities comparable to natural daylight, and its spectral power distribution is often inadequate for non-visual effects. To evaluate the biological impact of artificial lighting on circadian rhythms, it is essential to know the spectral distribution – and if it is not available, to require melanopic metrics from the supplier, which, unlike photopic metrics, account for the content of the cyan, or so-called melanopic, spectral region, according to the IALD document. One example is the melanopic DER (Melanopic Daylight Efficacy Ratio), a parameter that helps assess how closely a light source mimics natural daylight in terms of circadian stimulation.
Infrared light – the future of lighting design?
In connection with spectral composition, the document also mentions the importance of infrared (IR) and near-infrared (NIR) radiation. Although this component does not directly affect vision, it plays an important role in supporting mitochondrial function and, according to studies on cells and animals, can protect eyesight by modulating the harmful effects of short-wavelength light (violet, blue, and green). This could fundamentally impact future lighting technology and require a shift in how we view energy efficiency, which is currently based on the V(l) curve with a peak at 555 nm.
Excellent color rendering and no subliminal flicker
Other aspects affecting lighting quality include flicker and the Color Rendering Index (CRI). Flicker, or subliminal flickering of light, may not always be visible but can contribute to stress, discomfort, and negative reactions in sensitive individuals (e.g., people with migraines or those on the autism spectrum). We recommend choosing so-called flicker-free fixtures. CRI expresses the fidelity of color rendering. A high CRI contributes to visual comfort and a pleasant perception of the environment but does not, on its own, guarantee light quality if other key spectral components are missing.
Conclusion: Inspiration from architects and practical recommendations
Leading lighting designers emphasize that light is much more than just a tool for seeing; it is a key factor affecting our health, well-being, and quality of life. Their document also shows the way to incorporate not only aesthetics and functionality into lighting design but also deep respect for the biological needs of people. Therefore, when choosing a light fixture for daily use, choose one that mimics natural daylight – with a spectral profile rich in the cyan (melanopic) and red (photobiomodulating) regions, providing sufficient illuminance measured not only in photopic lux but also in melanopic lux (EDI lux). Don’t forget about the spatial arrangement of light fixtures based on the time of day and always select flicker-free lights with high CRI.
Mgr. Tereza Ulrichová, Spectrasol
Reference: International Association of Lighting Designers, IALD European Regulatory Affairs Working Group “Lighting Design for Health, Wellbeing and Quality of Light, A Holistic Approach to Integrative Lighting”, 2025. – We summarized it HERE.
Translated using AI
