The following factors should
be considered when purchasing a screen:-
These include the mounting hardware and the type of roller
assembly. Mounting hardware with some screens is such that
it cannot be positioned tight to the wall. Some roller mechanisms
require constant tension on the screen to keep it in position
- this can lead to distortion of the screen over time, and
is also less convenient than mechanisms which hold the screen
in the position to which it is unrolled.
Screen size will necessarily be a compromise in a church installation.
Particularly in a traditional church, a large screen may well
look out of place. A screen size which is too small will be
impossible to read for people at a distance, whereas a large
screen will be difficult for those who are too close to it
- especially if it is at a height above them. (Minimum recommended
viewing distance should be at least 1.5 times the height of
the screen - maximum recommended is 6 times the height of
There are a variety of screen materials available, the most
common two being PVC or similar plastics, and fibreglass.
(Cotton may also be used). Fibreglass screens are obviously
stronger than the cheaper plastic types, and hold their shape
better over time. They are less inclined to curl at the edges.
It is also important to select a seamless screen, as some
manufacturers have welds in the plastic to reduce manufacturing
costs, but the joins are visible, and become more obvious
as the screen ages.
The screen surface is an important element in determining
how visible a projected image will be. As a rule, the more
reflective a screen is (screen "gain"), the narrower
the viewing angle will be. Screen surfaces fall into three
categories - diffusion, reflective, and retro-reflective.
Diffusion screens have a gain of 1, and can be used in virtually
any circumstances, provided bright light (apart from the projector!)
does not illuminate them. Reflective screens with a gain of
around 2, are best used when the projector can be mounted
at high level above the screen - they appear brighter, but
have a slightly narrower field of vision. Retro-reflective
screens (gain around 2.8) have tiny beads - usually glass
- embedded in the screen and appear to be very bright. Unfortunately
they suffer from very narrow fields of vision.
Research has shown that under normal circumstances,
400 lux of reflected light from a screen is a reasonable level
for showing images under typical ambient light levels. Lux
= Light Output (in lumens) x Screen Gain, divided by Screen