Rear Screen Installations - Runco Video Xtreme VX-40d Owner's Operating Manual

Section 2: Installation and Setup

Rear screen installations

There are two basic types of rear screens: diffused and optical.
A diffusion screen has a surface which 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. This type of screen is
suitable when a wide viewing angle is required but there is low ambient room lighting.
Optical screens (e.g. Fresnel Lenticular) 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. The size of the
room and viewing distance are the defining factors; a rule of thumb is that the primary
viewing distance be 1.5 x screen width.
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).
11