compound-contour reflectors, fluorescent
lamps have difficulty projecting a high inten-
sity toward the bottom of a wall. The follow-
ing guide will be helpful in providing
approximate visual uniformity with linear T5,
T8, and T12 fluorescent lamps.
When using fluorescent lamps in stan-
dard reflector channels to light walls, display
boards, or draperies, place the channels at a
1:4 ratio of distance away from the lighted
surface to the height of the wall (figure
12.32). Luminance at the bottom will be
about one-tenth of the luminance at the top.
For many applications, the resulting percep-
tion of near uniformity is adequate.
Luminaires placed closer than the 1:4
ratio, calledgrazing light, emphasize surface
texture and low sculptural relief. But this
may also increase the awareness of irregu-
larities and lack of flatness of the lighted sur-
face. Additional frontal light, direct or
indirect, reduces this problem by filling in the
minute shadows cast by the irregularities.
When lighting from two opposite sides,
or from four sides, place the channels at a
1:6 ratio of distance away from the lighted
surface to the height of the wall. The 1:4 and
1:6 placement ratios are also applicable
when fluorescent channels are mounted ver-
tically (figure 12.33).INTERIOR LIGHTING FOR DESIGNERS
Figure 12.30Typical incandescent raceway wall-washer system.