licht.wissen No. 01 "Lighting with Artificial Light"

licht.wissen 01
Lighting with Artificial Light
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Direction of light and modelling
Without light we cannot make out objects; without shadows we see objects merely as two-dimensional images.
Only the right distribution of light and shade ensures that faces and gestures, surfaces and structures can be
accurately discerned.
[48] Directional light and the correct distribution
of light and shade reveal the details of
the figures.
[49 + 50] Distracting shadows should be
avoided if the light comes mainly from
above left (for right-handed people – or from
above right for left-handed people).
[51] In order to avoid stark shadows
in sports halls, the lights are arranged so
that their beams cancel out each other’s
shadows.
A pleasant light climate is created when the
people, architecture and interior furnishings
are illuminated in such a way that shapes
and surface structures are clearly visible:
distances can then be easily estimated, facilitating
orientation within the room.
A mixture of diffuse light (such as indirect
light on walls and ceilings) and directional
light (such as direct luminaires or downlights)
achieves optimum visual results and
contributes to a pleasant visual climate.
Conversely, a bright room with nothing but
diffuse lighting and no shadows leaves a
monotonous impression: the lack of orientation
makes us feel uncomfortable. By
contrast, point sources of extremely directional
light create strong shadows with
stark edges. It is almost impossible to see
anything in these stark shadows. They can
give rise to optical illusions which often
constitute a source of danger, for example
when using tools or machines. The same
applies for unsuitable stair lighting.
Visual communication
A precondition for good visual communication
is for objects and faces to be recognized
quickly and easily. In rooms in which
people move and work, DIN EN 12464-1
therefore stipulates an average cylindrical
illuminance – E Z of at least 50 lux. In areas
where good visual communication is especially
important, such as in reception areas,
shops and schools or in conference rooms,
150 lux are recommended as an average.
DIN EN 12464-1 cites modelling as an important
quality criterion for the 3D perception
of people and objects. It describes the
relationship between cylindrical and horizontal
illuminance at a particular point and
should be between 0.30 and 0.60.
Light direction
Directional light can emphasize visual details.
However, stark and intrusive shadows
(such as those caused by point sources of
light) should be avoided. The light direction
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