Common practice in lighting design still relies on the quantity Lux (lx), which expresses the intensity of light falling on a surface. However, this measure is based on the so-called photopic spectral sensitivity curve of the eye, defined back in 1924. This curve reflects only the response of the cones in the retina, i.e., our ability to see details and colors under daylight, with peak sensitivity in the green-yellow range (around 555 nm).
Modern photobiology has shown, however, that the eye does not function solely as a camera, but also as a sensor for our biological clock. This function is provided by intrinsically photosensitive retinal ganglion cells (ipRGCs) containing the photopigment melanopsin. These cells do not respond to brightness, but to specific wavelengths in the blue region of the spectrum (peaking around 490 nm). This is precisely where standard lux measurements fail, as they ignore this biologically crucial part of the spectrum.
This is where a new metric according to the international standard CIE S 026 comes into play, referred to as Melanopic EDI (Equivalent Daylight Illuminance), or simply “melanopic lux.” It does not indicate how bright we perceive the light, but how effectively it can activate our circadian system, suppress the production of the sleep hormone, and support cognitive functions of the brain.
A fundamental problem of conventional LED fixtures lies in their physical design. Typical LED sources generate white light using a blue chip (around 450 nm) and a phosphor. Between these two peaks, a spectral dip (the so-called cyan gap) occurs precisely in the melanopic range of 480–490 nm, which our circadian system is tuned to. The result is light that can have a high lux value (visually bright) but a very low melanopic value (biologically ineffective).
Spectrasol Technology eliminates this shortcoming. Thanks to a patented spectral composition, we fill the blue region of the spectrum with energy similar to sunlight. This allows us to achieve high Melanopic EDI values without drastically increasing visual brightness, which could lead to glare. Spectrasol thus delivers the necessary biological signal to the body while maintaining maximum visual comfort, something conventional LED sources cannot achieve due to physical limitations.
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