Front Projection and Rear Projection Systems
Front projection system: The projector is positioned on the viewer's side, and projects images from the
front of the screen.
Rear projection system: The projector is installed behind the screen, and projects images from the back
of the light-transparent screen.
Characteristics of Typical Screens for Front Projection Systems
Ultra-fine glass beads on the screen surface reflect the light
from a projector in the incident direction so images are bright
and clear at normal viewing positions.
However, since the diffusion characteristic is restrained to a
certain degree, the viewing angle is limited. This type of
screen is used with floor-standing projectors.
- Gain at center: 1.9 to 2.6
Because the pearlescent screen partially suppresses the
reflection of light entering in the opposite direction at an angle
equal to the incident angle of the projected light, it provides
bright, crisp images at the viewing position when a
ceiling-mounted projector is used.
- Gain at center: approx. 1.9
Since this screen scatters the light from a projector in all
directions uniformly, it provides a wide viewing angle, allowing
people to enjoy high-quality images from a broader viewing
However, due to its low screen gain, it is inferior in picture
- Gain at center: approx. 1
The screen size, or screen type, represents the diagonal
screen length in inches.
One inch equals 2.54 cm.
The ratio between the screen width and screen height is
4:3 for NTSC-size screens, and 16:9 for wide screens
such as the Hi-Definition system (HDTV). This is called
the "aspect ratio."
Using the aspect ratio, the width and height of a screen
can be calculated from the screen size.
The appropriate distance from the screen to
the front row of the audience is 2 to 3 times
the screen height.
A screen whose width (W) is 1/4 to 1/5 the
depth (D) of the room is generally considered
to be appropriate in size for that room.
For example, if the room measures 10 m in
depth, an appropriate screen width is 2.5 m
based on the ratio of 1/4. When selecting a
screen with the aspect ratio of 4:3 for that
room, an appropriate screen size would be
either 120 or 130 inches.
Check to see if the ceiling height allows the
installation of a screen of the size determined
as described above before making the final
selection of screen size.
When a screen is affected by external light, the
contrast decreases and the projected images
The contrast ratio indicates the magnitude of
this effect, and it is a ratio between video peak
(highlight) brightness and black level
When the interference of external light is
strong, the contrast ratio lowers and it
becomes difficult to obtain beautiful images.
How to Improve the Contrast Ratio
Reduce the interference caused by external
Make the area around the screen dark.
Use downlights. Reduce the projection image
Use a screen with directional characteristics,
and block external light entering from the
same direction as the projected light.
Change the room color to a darker tone.
More about screens next page
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Home Theater - Projection Screens
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