Interior Lighting for Designers

visual tasks. For comfort and ease of adap-

tation, make the ambient illuminance at

least 33 percent of the task illuminance.

VDTs

VDT screens present a particular challenge

for designers. Almost all VDT screens have a

dark, glossy, or satin surface that reflects

images of the surrounding space; the opera-

tor will see luminaires, ceilings, walls, or win-

dows as elements of excessive brightness

reflected in the screen (figure 13.13). The

designer must carefully select and locate

luminaires to minimize reflected images.

VDT tasks often require an almost hori-

zontal line of sight when viewing the screen.

Because of this, a large area of the ceiling

will be in the field of view in large open

offices. It is critical to minimize variation in

luminance on the ceiling plane in order to

prevent discomfort glare (figure 13.14).

With well-designed direct luminaires,

the luminance of the aperture will be equiva-

lent to the luminance of the ceiling. This

results in minimal brightness contrast

DESIGN

Figure 13.12Task-ambient (nonuniform) office light-
ing layout.

Figure 13.13Normal range for reflected line-of-sight angles in a VDT (65° to 110° from vertical).