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NOTE: Lenses for this projector are designed primarily for use with flat screens, but
the projector 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.
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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.
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.
Screen size (image size) may be from approximately 5 to 50 feet diagonal, depending
on the lens you are using. For instance, a 0.8:1 lens can produce a 5 to 25 foot image
size, whereas a 7-15:1 zoom lens produces a 10 to 50 foot image 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. 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.
NOTES: 1) Screens with aspect ratios of 4:3 are typically specified by diagonal size,
but screens having other aspect ratios are not always specified by diagonal size. 2)
Stated screen sizes below refer to the diagonal size of a 4:3 screen.
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Aspect ratio describes the
proportion of the screen
and is expressed as the
ratio of width to height,
such as "4:3" or "5:4" (see
right). Although image size
and image aspect ratio can
both be adjusted quickly
through projector software,
it is still a good idea to
choose a screen aspect ratio
which is most appropriate for your projector—for the Mirage 10000, use a 4:3
screen. Ideally, to exactly fill a screen with an image, the aspect ratio of the screen
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