Rear Screen Installations; Screen Size; Screen Aspect Ratio - Christie CP2000-XB Setup Manual

Rear Screen Installations

There are two basic types of rear screens: diffused and optical. A diffused rear screen has a surface that spreads
the light striking it. Purely diffused screens have a gain of less than 1. The main advantage of the diffused
screen is its wide viewing angle, similar to that of a flat screen for front screen projection. Optical rear 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, and creates a viewing cone similar to that of a curved front screen installation.
To summarize, optical screens are better suited for brightly lit rooms where the audience is situated within the
viewing cone. Diffused screens may be better suited when a wide viewing angle is required but there is low
ambient room lighting.

2.2.2 Screen Size

Screen size (image size) may be up to 145 feet across, depending on your lens and ambient light level. Choose
a screen size appropriate for your lens and application. Keep in mind that if the projector will be used to
display much 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. In other words,
small text that is simply located too far from the eye will be illegible no matter how sharply and clearly it is
displayed. NOTE: Screens/images are most described according to their horizontal (
Aspect ratio is also specified if it is anything other than 4:3 (see below). The older diagonal screen size
typically used for 4:3 displays such as televisions and monitors is less commonly used for large projection
screens.
Table 2.1 Matching Lenses to Screen Size
Application
1.25 – 1.45:1 zoom
1.45 – 1.8:1 zoom
1.8 – 2.4:1 zoom
2.2 – 3.0:1 zoom
3.0 – 4.3:1 zoom
4.3 – 6.0:1 zoom
5.5 – 8.5:1 zoom

2.2.3 Screen Aspect Ratio

Aspect ratio describes the proportion of the display and is expressed as the ratio of width to height, such as 5:4
or 16:9. Typical aspect ratios range from 1.25 to 2.35—the higher the value, the wider or less square the image.
See Table 2.2.
Table 2.2 Typical Aspect Ratios
Application
SXGA
35mm filmstrip
NTSC Video//XGA
PAL Video/XGA
HDTV Video
Letter box Video/Flat
Cinemascope
CP2000-XB Setup Guide
020-100250-02 Rev. 1 (06-2009)
Screen Width
10-121 ft.
8-102 ft.
6-83 ft.
5-66 ft.
3-49 ft.
2.5-35 ft.
2-27 ft.
Aspect Ratio
1.25 (5:4)
1.32 (4:3)
1.33 (4:3)
1.33 (4:3)
1.78 (16:9)
1.89 (2048 x 1080)
2.35
Section 2: Installation & Setup
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) screen width.
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