Lighting (Lux, Kelvin and Biological Completeness)
Light enables sight. Proper light improves visual acuity, enabling more effective cleaning, better soil removal, and reduced exposure to contaminants. Increasing access to natural or biologically complete lighting has been shown to support productivity, comfort, and overall health for workers and occupants.
A handheld light meter can measure brightness from 0–200,000 lux and visible color “temperature” in Kelvin (K) from approximately 2,000–10,000K. Typical office lighting ranges from 300–500 lux, while daylight ranges from 10,000 to over 100,000 lux depending on conditions. Higher light levels enable better visibility and more effective cleaning. Natural daylight typically measures between 5,000–6,500K. While adequate brightness improves visual performance, brightness alone does not equal healthy light.
Lux and Kelvin alone do not define the complete, “full-spectrum” of light, and light is not merely illumination—it is biological nourishment. Just as food quality affects human health, the quality of light determines how well the body, brain, and visual system function. Research nonprofit Science of Light refers to this concept as photo-nutrition: the complete range of light wavelengths required to support human biology, not just vision.
True Full-Spectrum Light = Complete Photo-Nutrition
Sunlight is considered a truly “complete” full spectrum because it delivers a balanced continuum of both “visible and invisible” wavelengths. Most modern LEDs and fluorescent systems lack essential, near-infrared (NIR) wavelengths, creating a form of photo-nutritional deficiency.
Full-Spectrum Light and the Role of Near-Infrared
Full-spectrum light—commonly equated with sunlight—has long been associated with improved mood, energy, sleep quality, and cognitive performance. A major study in the American Journal of Psychiatry showed that individuals exposed to full-spectrum lighting experienced significant improvements in mood and vitality. Research published in the Journal of Clinical Sleep Medicine demonstrated that exposure to biologically appropriate lighting supports circadian alignment, improved sleep, and greater daytime alertness. Educational studies show improved concentration, test performance, and reduced hyperactivity under full-spectrum lighting, while occupational health research reports fewer headaches, higher energy levels, and increased job satisfaction.
Emerging research now clarifies that naturally “balanced” full-spectrum light must include invisible near-infrared (NIR) wavelengths, which are abundantly present in natural sunlight but largely absent in most LED and fluorescent lighting systems.
Near-infrared light (approximately 700 to 2500 nm) penetrates ocular tissues and has been shown to:
• Support mitochondrial function in retinal cells
• Improve cellular energy production (ATP)
• Reduce oxidative stress and retinal inflammation
• Potentially protect against light-induced retinal damage associated with blue-heavy artificial lighting
Studies in photobiomodulation and ophthalmology indicate that the absence of NIR may contribute to retinal strain and inflammation, particularly when the eye is exposed repeatedly to high-intensity visible light without the balancing, protective effects of longer wavelengths found in sunlight.
Toward a More Complete Lighting Quality Index
Just as diet quality can be graded, light quality can be indexed based on both visual and biological completeness: cleaning and facility professionals can use a Lighting Quality Index to evaluate indoor light environments beyond brightness alone and include:
1. Brightness (lux) – Sufficient illumination for tasks and cleaning
2. Color balance (Kelvin) – Balanced visible spectrum
3. Spectral completeness – Inclusion of UV (trace), visible, and near-infrared wavelengths
4. Biological safety – Reduced retinal stress and inflammation
5. Circadian support – Alignment with natural light cycles
6. Visual comfort – Reduced eye strain and fatigue
7. Cognitive performance – Alertness, focus, and mood
8. Energy regulation – Mitochondrial and cellular support
9. Environmental realism – Closeness to natural sunlight
10. Total photo-nutritional value – Light that nourishes, not just illuminates
Lighting that includes the natural balance of both visible and invisible wavelengths that more closely replicate sunlight, improves both visual performance and biological safety, while supporting long-term eye health and whole-body well-being. Light should not merely allow us to see—it should help us thrive.
Information above provided by Ken Ceder, Executive Director, Science of Light, a 501(c)(3) nonprofit organization.