Health
Day and night naturally set the rhythm for almost all organisms. All bodily functions - including those of human beings – respond to the circadian cycle. |
For example, the human organism only produces the hormone melatonin in the dark.
"Less melatonin means poorer sleep and more stress. This continuous stress can weaken the immune system and thus impair human health," says Dr. Peter Heilig of Vienna Medical University. A number of studies even suggest that melatonin can offer a degree of protection against cancer.
- On the left a dazzling spherical luminaire, with well shielded light fittings in the background
Road safety (glare and contrast vision)
We all know what it is like: Your eyes have adapted to the dark, and suddenly you are confronted with a bright white light; the glare has an incapacitating effect for several seconds. This is obviously a problem for road safety. A quick glance into the brilliant bluish white light of a car’s headlights or the street lights or some other lighting installation causes dazzle and disturbs the process of adaptation and scotopic or twilight vision. In order to avoid glare, due attention must be paid to the photometric properties of both the luminaires and the light sources.
Every visually perceived object is surrounded by an aura that reduces contrast. Yellow filters improve contrast. That is why yellow filters are used for ski goggles for misty conditions, shooting glasses, pilot’s glasses, spectacles for the visually impaired and also for intra-ocular lenses. Yellow light sources produce less glare than bluish-white light sources; they improve contrast vision and so contribute to safety on the roads (Dr. Peter Heilig).
PDF (Impaired Perception in Driving and Sport)
PDF (Wie viel Licht benötigen wir?)
PDF (Blendung aus dem Blickwinkel des Augenarztes)
http://www.youtube.com/please turn off DRL
Security and crime
Artificial light is an integral part of our culture. Lighting at night for public areas satisfies a basic need; street lighting offers orientation and security. When used correctly and in the right amount, artificial light can also make a contribution to a city’s atmosphere and aesthetics.
Light has great symbolic value; many people associate good with light and evil with dark. So it not surprising that the majority feel uneasy in dark side-streets. Public lighting promotes a feeling of security that is primarily subjective – as there is no objective evidence indicating a relationship between lighting and crime rates.
http://www.britastro.org/dark-skies/crime...