(c)  ro - architecten
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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.