"And Elokim said: Let there be light"
We all value light and realize its importance for seeing
around us, but its significance extends far beyond simply
being able to see what is in front of our eyes.
Lighting can affect our efficiency and the way we perform
tasks, such as reading and housework. It can also affect our
mood, our attention span, our tolerance, our health and
safety and the way we relate to others.
Until the invention of the tungsten-filament incandescent
lamp, people relied on sunlight and light from burning
candles, oil and gas. Over the past forty years, these have
largely been replaced by fluorescent tube lamps, halogen
lamps and various forms of gas-discharge lamps which give out
more light than the original incandescent lamps.
Many people assume that the brighter a lamp is, the better it
is, but brightness is only one of many factors that can
affect the suitability of lighting. Apart from the brightness
of the light source and its angle of illumination, we need to
consider the brightness of the light on the work surface, its
uniformity across the surface, the way the illumination is
distributed within the room, glare, the color of the light
and its degree of flicker.
Another factor to consider is that sensitivity to light tends
to decrease with age. This is due to clouding of the lens and
fluids within the eye. For example, a person in his forties
will need four times brighter light for comfort than a child.
Therefore, an old age home will need a much higher level of
illumination than a school.
Regular magnetic ballast fluorescent lights flicker at the
rate of the electric current supply which in Israel and
Europe is at the rate of 100 flickers per second. Children
and adults might be adversely affected by this flicker and so
such people would find it more relaxing to be in a room lit
by incandescent lamps, which scarcely flicker, or electronic
fluoresent lamps, with a flicker rate is too high to be
detected.
For regular tasks such as reading and writing, contrary to
popular belief, above a minimal level of illumination,
increasing brightness does not improve performance or
efficiency. On the contrary, especially regarding young
children, increasing brightness might overstimulate them and
make them hyperactive.
The eye automatically adjusts itself according to the
brightness of what it is seeing. Therefore, if a bright light
is within the line of vision, it will cause the eye to lower
the apparent level of illumination. Therefore, when reading
when a bright light is in the line of vision, the bright
light will cause the page to appear darker than if the light
was either placed out of the line of sight or replaced by a
less intense light.
The most pleasant light comes from lamps shielded from direct
view but aimed to illuminate the ceiling and walls. The color
of the light emitted by the lamp varies according to the type
and the age of the lamp. Even the coloration of daylight
varies according to the time of day. Some lamps emit light
that is distinctly colored, such as the intense yellow of
sodium lamps or the blue of mercury lamps. Because their
coloration is limited to a narrow band of colors, they are
very efficient but unpleasant for indoor use.
Other types of lamps appear to emit white light, but still
they might not match the pleasantness of sunlight. However,
some manufacturers produce "full spectrum" fluorescent lamps
that they claim match the coloration of sunlight very
closely. Such lamps also often emit a small amount of ultra-
violet light that might be beneficial, especially to
schoolchildren and older people.
When discussing the effect of lighting in the classroom, one
remedial teacher told me that when she changed the
fluorescent lighting in her room to full spectrum lighting,
she noticed a significant reduction in behavioral and
learning problems! However, full spectrum tubes are more
expensive than regular tubes and less readily available.
Indirect sunlight is still the cheapest and most pleasant
form of lighting and is the standard against which all other
forms of lighting are compared. So, if you have large
windows, you do not need to feel compelled always to turn on
the lights. Most tasks, including reading and writing, can be
performed efficiently in regular daylight and you might feel
more relaxed and better able to concentrate.
