Healthful lighting is the technology of programming the light intensity and spectrum delivered by a light fixture to suit the Circadian Rhythm of human body, or also known as "body clock", while minimizing the harmful effect caused by "Blue Light Hazard". The light pattern during the 24-hour cycle to best suit the body clock is to follow the sun rise and set.
Light source emits specific spectrum and certain level of light intensity, which are the determining factors to calculate the Circadian Stimulus (CS). The light intensity is required to be measured on a vertical plane, or known as vertical illuminance. Its unit is either Lux or foot candle. The light meter or phone camera is placed vertically at the eye level to measure the vertical illuminance.
The height of 1.2m (~4 ft) and 1.6m (~5 ft) above the ground are recommended for the sitting and standing position respectively, when the vertical illuminance reading is taken.
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