Light Academy - advanced level
Spectral Power Distribution
Two light sources can appear almost identical to the human eye while having very different spectral compositions.
Spectral Power Distribution (SPD) describes exactly how much energy a light source emits at each wavelength across the spectrum. It is one of the most important tools used by lighting scientists because it reveals information that brightness and color temperature alone cannot provide.
Understanding SPD helps explain why two lamps with the same color temperature may create very different visual and biological environments.
Measuring light
Not all light measurements describe the same thing.
Lux measures how bright light appears to the human eye, while melanopic metrics attempt to estimate how strongly light stimulates the biological pathways involved in circadian regulation.
As research into light health has evolved, scientists have developed new ways to evaluate lighting environments beyond traditional brightness measurements.
These tools help researchers better understand how light may influence both vision and biology.
Our spectroradiometer (image) measures blue light hazard (Ebi), color temperature (Kelvin), color rendering index (CRI), and much more.
Photobiomodulation
Photobiomodulation is the scientific term used to describe how certain wavelengths of light may interact with biological tissues.
Researchers are particularly interested in red and near-infrared wavelengths because they appear capable of reaching tissues beneath the skin and influencing cellular processes.
One area of investigation focuses on mitochondria—the structures responsible for producing much of the body's cellular energy.
While research continues to develop, photobiomodulation has become one of the most active fields within light-based health science.
Irradiance
In light therapy, intensity is only part of the equation.
Scientists often measure irradiance, which describes how much light energy reaches a specific area. Exposure time is equally important, since the total dose depends on both intensity and duration.
This helps explain why stronger light is not always better. The relationship between dose and response can be surprisingly complex.
Understanding these concepts is essential when evaluating light therapy devices and scientific studies.
Cellular penetration
Near-infrared light lies just beyond the visible red portion of the spectrum. Unlike visible light, these wavelengths cannot be seen by the human eye, yet they are capable of penetrating biological tissues more deeply than many visible wavelengths.
This deep cellular penetration allows the light to directly reach the mitochondria, the cell's energy factories responsible for producing ATP (adenosine triphosphate)—the vital fuel that powers our bodies.
This characteristic has made near-infrared light a major area of interest in photobiomodulation research. Scientists continue to investigate how different wavelengths interact with skin, muscles, blood vessels, and other tissues throughout the body.
Violet light - the future?
Most discussions about healthy lighting focus on reducing blue light exposure after sunset.
However, some researchers are exploring whether violet light may offer an alternative approach. Although both violet and blue light occupy the short-wavelength region of the spectrum, they interact differently with the eye and may produce different biological responses.
Research in this area is still emerging, but it highlights an important idea: the future of lighting may depend not only on reducing certain wavelengths, but on understanding how the entire spectrum influences human biology.
