Electrohome VistaGRAPHX 10K, User Manual, Page: 9 / 127

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Curved screens have gains larger than 1 (due in part to the screen material) and
viewing angles much less than 180°. Most curved screens have different
horizontal and vertical viewing angles. Incident light does not reflect equally in
all directions. The reflected light concentrates in a conical volume or "viewing
cone". Audiences within the viewing cone see a brighter image than that from an
equal area on a flat screen. Audiences outside the viewing cone see a dimmer
image.
NOTE: Vista
GRAPHX
10K lenses are designed primarily for use with flat screens.
However, the projector depth-of-field range allows the lens to be focused on
curved screens as well. Focus remains sharp in the corners, however there may
be significant pincushion distortion, primarily at the top of the screen.
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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 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 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.