DG 111O-3-1O6
Front Projection
Rear Projection
A Projection Source
B Screen
C Seating Area
Figure 3-16
Comparison of Space Utilization
Front and Rear Screen Systems
students a good view of the screen, and prevent
sloped floors. In rooms designed for television viewing,
students' heads from casting shadows on the screen
an alternative is to install the television sets along
perimeter walls.
when using rear projection. Ceilings higher than 12
feet are seldom required, but should not be less than 9
feet high. If a projection screen is used, the required
(2) Square Room.
A room of approximately square shape is best for A-V
ceiling height, C (feet), can be found using the
presentations; excessive width or length will cause visua1
equations below and assuming that the bottom of the
and acoustic distortions.
screen will be placed 4 feet above the floor and that
the distance between the top of the screen and the
ceiling will be 6 inches. For horizontal image formats,
(3) Image Distortion.
where the image height is less than or equal to the
As the distance of the viewer from the room's center
screen width, W (feet) is divided by 1.33:
increases, so does the image distortion. Figure 3-18
W
indicates the amount of distortion occurring at various
viewing angles.
where the room length, L (feet), is 6W. This can be
(4) Relationship Between Viewing Area, Screen Height, simplified to establish a direct relationship between L
and C:
and Ceiling Height.
L=8C36
Generally, the screen height is determined by the
For vertical image formats, where the image height is
room's ceiling height. The screen must be at least 4
greater than or equal to the image width:
feet above the floor and typically 6 inches from the
C=4.5+W
ceiling. A screen width is then selected so that the
and
screen's proportions are compatible with the
L=6C27
proportions of commonly projected images. The screen
If vertical formats (slides) will also be used, the screen
width, together with the nature and location of the
projection source, establishes the recommended viewing height value H is equal to W, and will require
additional height.
area. The ceiling should be high enough to insure
necessary image sizes on the project screen, provide all
3-14
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