thereby retaining full contrast and color saturation in the
MATTE SCREENS. Matte screens diffuse light
evenly in all directions. Images on matte screens appear
almost equally bright at any viewing angle. To avoid
distortion caused by the viewing angle, the viewers
should be no more than about 30 degrees from the center
line of the projection axis; they should be no closer than
two times the image height (2H) from the screen.
LENTICULAR SCREENS. Lenticular screens
have a regular pattern of stripes, ribs, rectangles or
diamond-shaped areas. The pattern is too small to be
seen at viewing distances for which the screen is
designated. The screen surface may appear to be
enameled, pearlescent, granular metal or smooth metal,
and it may or may not have a coating over the reflective
By controlling the shape of the reflecting surfaces,
lenticular screens can reflect nearly all the light from the
projector evenly over a fan-shaped area about 70
degrees wide and 20 degrees high. People seated farther
to the sides of the screen than the 70-degree angle or
above or below the 20-degree angle may not see an
image; no image-forming light is wasted outside the
viewing area. Many lenticular screens provide an image
three or four times as bright as a matte screen.
BEADED SCREENS. Beaded screens are useful
in long, narrow rooms. They have white surfaces with
embedded or attached small, clear glass beads. Most of
the light reaching the beads is reflected toward its
source. Thus a beaded screen provides a very bright
image for viewers seated near the projector beam. As a
viewer moves away from the beam, the image
brightness decreases. At about 22 degrees from the
center line of projection, the image brightness on a
beaded screen is about the same as that on a matte
screen. Beyond this angle it is less bright than on the
Since nonimage, or stray light, is also reflected in
the general direction from which it comes, stray light
falling on a beaded screen from a viewers position at
the side of a room can be a major problem.
REAR-PROJECTION SCREENS. Rear-pro-
jected images have the same requirements for image
brightness, size and contrast as front-projected images.
Rear projection has advantages in some situations and
disadvantages in others.
A person or object in front (on the viewer side) of a
rear-projection screen does not interfere with the
projection beam. This makes rear projection useful
when the projector must be concealed, as in displays. It
permits close examination of the screen image. Rear
projection may provide advantages in image contrast
and color saturation in a lighted room.
Rear projection also has its disadvantages. With
conventional projection, the space over the heads of
viewers is usually used for the projector beam. With rear
projection, the projection beam is on the opposite side
of the screen from the viewers. Consequently, space for
the beam must be provided outside the viewing room
behind the screen. To reduce space requirements in rear
projection, you should use short focal length lenses.
More commonly, mirrors are used to fold the
projection beam. Both methods are likely to reduce
image brightness and quality.
Another important consideration in rear-projection
screens is the darkness of the screen as seen by reflected
light. As with front projection, the highlight brightness
of the image should be as bright or brighter than other
areas within the viewers peripheral vision.
If the image is to be viewed in a well-darkened
room, there is no advantage in a dark-toned screen. If
the image is to be large, a light-toned screen is usually
preferable since it absorbs less image light than a
You can achieve optimum viewing by using the
following accepted standards for audience placement in
relation to the screen, as shown in figure 6-9.
Line of Vision
In planning the space arrangement, the speaker
should not stand in the line of vision. The lectern should
be located to one side of the screen, leaving a clear view
of two thirds of the stage area and only partially blocking
the remaining third. On the opposite side of the screen
from the lectern, A-frames, flipcharts, dry marker or
chalkboards, and so forth, can be set up for optimum
Proper lighting is
Without question, the
brilliant the image on
important to relaxed viewing.
less the room light, the more
the screen and the greater the
contrast. On the other hand, brilliance and glare can be
annoying and cause eyestrain. A proper level of room
light reduces the contrast and permits viewing with a
minimum of strain.