Interior Lighting for Designers

the perimeter provides shielding from all
directions.
Louversare a series of baffles or shield-
ing elements placed in a geometric pattern
to provide shielding from many directions
with minimum interference to the desired
beam distribution (figure 9.23).
Shielding conceals the lamp and con-
trols glare within a zone called theshielding
angle. This is the maximum angle that the
eye is raised above horizontal without seeing
the light source beyond the shielding system
(figure 9.24).
Although baffles and louvers conceal
the light source from direct view within this
specified zone, horizontal work surfaces are
still directly exposed to the source. The mir-
rored image of the light source becomes a
source ofreflected glarefrom glossy paper,
photographs, objects behind glass, and pol-
ished tabletops (figure 9.25).
Baffles and louvers may be black or
made from reflective and transmitting mate-
rials. The intensity of light directed toward
the eye is determined by the luminance of
these surfaces. The choice of materials is
based on various considerations including

visual comfort and design harmony with the

space (figure 9.26).

To achieve concurrent glare control and

lamp concealment with minimal change in

the diffuse beam, use open louvers, or plas-

tic or glass with a slight degree of diffusion.

Whether the beam is modified by diffuse

reflection or by diffuse transmission, the dis-

tribution of light is the same.

Reflectors

An opaque (light-blocking), concave reflec-

tor also functions as a baffle, which shields

the light source. Additionally, the reflector’s

shape affects the appearance of the visible

interior surface. If light is redirected toward

the eye, the result is high luminance and

unpleasant direct glare. If light is directed

downward and away from the eye, lumi-

nance is reduced and glare is avoided.

In the most efficient reflector designs,

source shielding is incorporated into the

contour design. This involves extending the

reflector surface to provide the necessary

shielding (figure 9.27).

As reflector depth is increased, total effi-

ciency is reduced because of absorption

LIGHT CONTROL

Figure 9.28Parabolic reflector used for glare control. Figure 9.29Parabolic reflector design for louvers and
baffles.