faces and the wall and floor), the borders of
interior space (figure 13.7). The evenly
lighted wall is perceived as an integrated
visual form (figure 13.8). The same is true of
the evenly lighted ceiling plane.
Lighting Vertical Surfaces
Vertical surfaces require special attention:
they are the first surfaces that we see upon
entering a space. Vertical surfaces define
the boundaries of the space; they are used
for displaying works of art and communicat-
ing a message. Clear perception of vertical
surfaces significantly impacts our perception
of the overall design.
Reliance upon formulas to provide a spe-
cific illuminance value on the horizontal plane
disregards the importance of vertical sur-
faces. Consequently, luminaires used for
ambient illumination often cast unanticipated
or undesired light patterns on the vertical sur-
faces, or leave them in relative darkness. If
not distracting, the resulting environment is
unintentionally dull and monotonous.
It is critical to anticipate where
downlight distributions will intersect vertical
surfaces.Scalloppatterns and similar irregu-
larities are to be minimized. Except for spe-
cial situations, a lighted surface is not
intended to be perceived as a form or sur-
face that is intersected by arbitrary patterns
of light; it is intended to be perceived as a
unified form.
Scallops of light are incompatible with
the plane form of the wall. Because the eye
is involuntarily attracted to areas that con-
trast with the ambient brightness, scallops
result in a disorienting pattern of superim-
posed light that confuses perception of the
visual form of the wall (figure 13.9).Figure 13.7A linear wash of light facilitates spatial clarity.