Runco Reflection VX-5c Owner's Operating Manual page 10

INSTALLATION AND SETUP
NOTE: Lenses for this projector are designed primarily for use with flat screens, but the projec-
tor depth-of-field range allows the lens to be focused on curved screens as well. While focus
remains sharp in the corners, there may be significant pincushion distortion, primarily at the top
of the screen.
Rear Screen Installations
There are two basic types of rear screens: diffused and optical. A diffused screen has a surface
that evenly 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. Fresnel lenticular 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.
To summarize, Fresnel lenticular screens are better suited for brightly lit rooms where the audi-
ence is situated within the viewing cone. Diffused screens may be better suited when a wide view-
ing angle is required but there is low ambient room lighting.
Screen Size
Screen size may be from 5 to 40 feet diagonal, depending on the lens you are using. For instance,
a 1.2:1 lens can produce a 5 to 25 foot image size, whereas a 4-7:1 zoom lens produces an 8 to
40 foot image size. Choose a screen size that 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 dis-
tance is less than 150 times the height of the letter. Small text located too far from the eye may
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. The aspect ratio of an image is the ratio of its width to its height. Standard television
has a 4:3 or 1.33:1 aspect ratio. For example, to display a television image 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).
Note: Screen size is often specified as diagonal size. Screens specified by diagonal size have
aspect ratios of 4:3. Screens with other aspect ratios, such as 16:9, are not typically specified by
diagonal size, instead they are specified by height and width.
Figure 2.1. Audience Coverage with Flat Screen
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