losses at the reflector surface. Because a
greater portion of the emitted light is brought
under control and redirected, however,
candlepower and useful lumens increase.
Parabolic reflectors are often used for
glare control. Little reflected luminance occurs
in the cross view of these reflectors because
most of the light is directed downward with
minimal light directed toward the eye; this
gives an impression of low brightness from
normal angles of view (figure 9.28).
Diffusion of the reflector surface causes
more light to be directed toward the eye. As
a result, luminance is increased when reflec-
tor surfaces are etched or brushed.
Parabolic reflector design is applied to
both reflectors and baffles. Figure 9.29
shows the pattern of light reflections for light
rays originating above the louver. Ideally,
light is reflected at an angle equal to the
shielding angle.
Well-designed, specular, parabolic lou-
vers provide equal or superior glare control
to matte-black or gray louvers, with greater
system efficiency because of the reduced
absorption of light.INTERIOR LIGHTING FOR DESIGNERS