120°—offer a more practical light distribu-
tion for many purposes. A luminaire with a
100° beam-spread, emitting most of its light
below acutoffangle of 40° from horizontal,
is offered by most well-designeddownlights.
This greater percentage of light at higher
angles increases incident light on vertical
surfaces,modelsfaces, and reduces the
concentration of brightness within the
space. Diffuse downward luminaires yield a
low-contrast setting (figure 3.5).
Aconcentrated upward(indirect) distri-
bution directs light toward the ceiling (figure
3.6). With light directed upward and the
downward component removed, the ceiling
becomes visually prominent. It also becomes
asecondary light sourcebecause of its reflec-
tive properties.Figure 3.1The seven directions and distributions of light.
Figure 3.2Concentrated downward (direct) distribu-
tion.
Figure 3.3An example of concentrated downward distribution.