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Light plays an essential
role in our ability to perceive the world around us; the
lighting system plays a critical role in how we perceive a
space and can even influence how we act in that space.
Lighting can affect performance, mood, morale, safety,
security and decisions.
The first step in producing
the right lighting design is to ask what the space is used
for. The lighting designer can then determine quantity of
light, color quality, brightness and direction.
It is beyond the scope of
this article to go step by step through the process of
producing a lighting design. Instead, we will review the
several ways that lighting professionals look at lighting
design, from the simple to the sophisticated.
Simple. One way is to
ensure that the lighting system 1) provides ambient
illumination for orientation and general tasks in the
space, 2) task illumination for local, more demanding
tasks, and 3) accent illumination to highlight
special objects of interest or to guide occupants. An
example of this scheme is an open office plan with
workstations; we might provide indirect fixtures to provide
ambient illumination, task lighting at the workstations for
work, and accent lighting to highlight pieces of corporate
art on the walls.
Standard. A typical
general approach to lighting design is, after determining
how the space is used, to provide general, localized
general, localized and task illumination to meet these
needs. General lighting provides a generally uniform light
level on the workplane throughout the lighted space.
Localized general lighting is similar but is tailored more
to the location of tasks in the lighted space. Localized
lighting, also called supplemental lighting, is used to
provide light to a specific area. Task lighting delivers
light tailored for a specific task.
Sophisticated. A
final way of looking at lighting design is more
sophisticated, focused not only on simply providing quantity
of footcandles for tasks with accent illumination for
highlighting, but also on the art of using light to produce
a desired effect.
To explain this last
approach, which deals with how the direction of light is
controlled, let us start with an object.
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Key Light.
When we shine a light on an object from a single
point source of light it is called key light; it
highlights contours on the object and creates
shadows; the exact effect depends on the angle of
the beam of light. Most of the time we want to
light the object to we can see its front. In these
cases, the light source may be best place in front
of and to the side of the object at an angle of
45°. |
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Fill Light.
While this scene effects drama, for our purposes we
will assume we need fill light. It can either be
directional or diffused. In our example we could
shine a directional light on the object from the
opposite direction of the key light, softening or
eliminating shadows depending on the strength of
the fill light relative to the strength of the key
light. We could also place fill light sources
behind the object to light the entire room evenly.
In the Figure below, we see the keylight
supplemented by a single fill light. |
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Silhouetting.
Suppose we wanted to emphasize the shape of the
object as a silhouette. In this event, we would
soften or even eliminate the key light and
directional fill light, and instead provide only
fill light, either intense or diffused, depending
on the clarity of the silhouette and the drama we
want to produce. |
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Uplighting.
Suppose we wanted to uplight the object. The effect
of uplighting is either very desirable or very
undesirable because it is unusual. Effects range
from intimate to eerie. A lot of landscape lighting
includes uplighting to accentuate bushes and
trees. |
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Sparkle And
Glitter Effects. To add an atmosphere of
elegance, we could add little lighting points of
interest in the form of sparkle or glitter. This
effect can be produced by either producing sharp
reflections on specular surfaces in the room
(sparkle), such as silverware in a restaurant, or
by making the light source itself a source of
interest (glitter) such as with a chandelier.
Beware of glare in such cases. |
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Grazing And
Washing Surfaces. On walls or on the surface of
an object, we can change the way light impacts them
so that we can produce different effects. Suppose
we have a brick wall with a rough texture that we
want to emphasize. We could graze the surface with
light, meaning the light would strike the surface
at a sharp angle. In this case, the light source
would be mounted close to the wall. Now suppose the
wall is smoother, and we want to emphasize that
smoothness. We could wash the surface with light,
meaning the light would strike the surface at a
wider angle. |
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The selection of strategy or combination of strategies
again will depend on how the space is used. In a retail
environment, it might be desirable to provide strong
keylighting to accentuate and dramatize key merchandise,
while in an office such strong concentrations of
accentlighting and shadowing might prove visually fatiguing.
Uplighting may work well in an intimate restaurant or to
highlight bottles of alcohol in a bar, but may make people
look sinister in the home or office. Sparkle and glitter may
work well in a restaurant, but might prove distracting in
many industrial work areas.
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