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(c)  ro - architecten update    Oct  2016
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Why does the kind of light we like changes during the day? Most offices  and factories are lit up by fluorescent lighting. For most of us, this is  quite acceptable. In the evening however, we don't like the fluorescent  light, at home or in restaurants and pubs, you will find incandescent  light sources or even candles when we want to create a real cosy  atmosphere. Nobody however will lit a candle at the office during the  day to make it more cosy there. In a pub, at closing time, there is one  simple way to get your customers out, simply turn on the fluorescent  lighting. Obviously there is a relation between the time of the day and  the kind of light we prefer or at least accept. I think we can explain a lot about our lighting needs by looking back to  where we came from. For centuries we lived under almost constant  light conditions, 365 days a year a rhythm of twelve hours daylight and  twelve hours darkness, with a natural returning pattern of light level and colour temperature. In this article I call this kind of light the "primeval  light". The relation between the amount of light and its colour  temperature was described by Kruithof. I tried to add a third dimension  to his curve, the biological time. Maybe this can help us making lighting  designs.
Light and Humans