perceive variations in haemoglobin oxygen saturation
and haemoglobin skin concentration, which determine
skin tone modulation. Furthermore it has been noted
that all trichromatic primates are bare faced or have
patches of skin exposed, allowing skin tone to be read.
Even more fundamentally, light is energy and as such
has a profound effect on our biological systems. Papers
published at Jefferson University in Philadelphia are
currently leading a body of evidence to show that
melatonin suppression is directly associated with blue
wavelengths of light. Results of these studies are already
being used by NASA to assist astronauts in regulating
sleep. But while several independent studies have
shown that exposure to these wavelengths can increase
alertness during the day, it has also been found that red
light is just as effective in increasing brain activity. So it
appears that melatonin suppression is not necessarily
needed to have an impact on alertness.
Researchers have also observed that there are certain
physiological reactions that seem to occur on exposure
to coloured lighting that are common irrespective of
culture or race. There is an impact on neurological
responses, on the autonomic nervous system and, as
mentioned, on the hormonal activity.
The colour red can raise blood pressure, pulse rate,
respiration and perspiration, and excite brain waves.
There is more muscular tension and greater frequency
of eye blinking. Blue effects are somewhat opposite:
lower blood pressure and pulse rate, less skin response
and a slowing down of neurological responses.
Reactions to orange and yellow are similar to those
provoked by red, but not as strong, and reactions to
purple and violet resemble those to blue. Green is
found to be the most neutral.
In photopic vision the eye is most sensitive to
greenish-yellow (ca 550nm) light. Psychologists Ferree
and Rand suggest that yellow illumination is most
comfortable for the eye followed by orange-yellow,
yellow-green and green. Deep red and violet are more
uncomfortable and blue is very difficult for the eye to
focus on and will cause objects to appear blurred and
as if surrounded by a halo.
The reason that the eye has trouble concentrating on
blue is that there are no blue-sensitive cones in the
fovea centralis – the source of our acutest vision. The
closed packed green and red-sensitive cones in the fovea
produce the best resolution, as the eye focuses most
on and will cause objects to appear
blurred and as if surrounded by a halo’
The 1918 Prince Edward, or Bloor, Viaduct is the longest bridge in
Toronto. A suicide prevention structure called Luminous Veil was
added in 2003 and lit by GVA Lighting with 600 RGB fixtures, here
seen in the blue state