lighting equipment must also be adjusted
(figure 13.24).
The placement of the light source
depends upon the medium, surface texture,
kind of frame, and enclosure (glass or plas-
tic) of the object. For flat works mounted on
a vertical surface, the optimum location for a
light source is usually at an angle of 30° from
nadir (straight down) to average eye level
(5 ft 3 in AFF) (figure 13.25).
An aiming angle of less than 30° (more
nearly vertical) creates disturbing shadows
from the frame and distorts the object
because it exaggerates its texture. An aiming
angle greater than 30° (more nearly horizon-
tal) results in reflected glare from the surface
of the object, washing out detail. This greater
angle also casts a shadow of the viewer on
the artwork and causes the luminaire to be a
source of glare to others moving through the
space.
For nonuniform wall lighting, point-
source object lights are ideal. When more
than one luminaire is required because of
the size of the work to be lighted, the square
rule applies once again: the luminaires are
spaced on centers closer than or equal to
the distance away from the wall. The dis-
tance from the wall varies with the ceiling
height (figure 13.26).
When a space with nonuniform vertical-
surface illumination has frequently changing
exhibits, a flexible lighting system is appro-
priate. Track systems are often selected
because the track luminaires are easy to
locate and aim (focus) as needed. The trackDESIGNFigure 13.22Lighting the vertical surface behind an object.