An interesting aspect is that although the ratio of day to night photopic illuminance is about 13:1 (200/15), the melanopic illuminance is approximately 65:1 due to using Amber coloured LEDs at night.
Melanopic illuminance variation during the day has a crucial influence on the human biological clock and circadian rhythms, resulting in significantly improved sleep quality at night and alertness at day time. Prisoners have welcomed this innovation and noticed the better sleep conditions after renovation.
Approximately 180 prison cells have been modified and the new luminaires have also been installed in the corridors.
Payback time for the new luminaires is expected to be less than 12 months.