Rear Screen Installations - Christie DS+60 User Manual

Section 2: Installation and Setup
2-4 Christie DS+60/DW30/Matrix 3000 User's Manual

Rear screen installations

There are two basic types of rear screens: diffused and optical.
A diffused screen has a surface, which spreads the light striking it. Purely diffused
screens have a gain of less than one. The main advantage of the diffused screen is its
wide viewing angle, similar to that of a flat screen for front screen projection. This
type of screen is suitable when a wide viewing angle is required but there is low
ambient room lighting.
Optical screens take light from the projector and redirect it to increase the light
intensity at the front of the screen. This reduces it in other areas. A viewing cone,
similar to that of a curved front screen installation is created. This type of screen is
better suited for brightly lit rooms where the audience is situated within the viewing
cone.
Screen size
Choose a screen size, which is appropriate for your lens and application. Keep in mind
that if the projector will be used to display text information, the image size must allow
the audience to recognize all text clearly. The eye usually sees a letter clearly if eye-
to-text distance is less than 150 times the height of the letter. Small text located too far
from the eye will likely be illegible at a distance no matter how sharply and clearly it
is displayed.
To fill a screen with an image, the aspect ratio of the screen should be equal to the
aspect ratio of the image (expressed as the ratio of its width to its height). Standard
video from a VCR has a 4:3 or 1.33:1 aspect ratio. For example, to display a VCR
output with a 4:3 aspect ratio onto a 10-foot (3m) high screen, the width of the screen
must be at least 13.3 feet (4m).
013-100149-02 Rev. 1 (01/07)