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 6.2.4
Options for Enhanced Capabilities.
6.2.4.1 Zoom Lenses. For surveillance applications where the FOV should be
varied, use of a motorized automated adjustable FOV or "zoom" lens is
appropriate. The variable focal length of the zoom lens permits change in
FOV without change in lenses. Many models are available, but generally a
five to 10 times change is possible for the FOV and is accomplished by
operator remote control. At the same time, as the lens "zooms" in or out,
the depth of
Table 12
Monitor Size Selection
RECOMMENDED
VIEWING DISTANCE
MONITOR SIZE
LESS THAN 14"
5"
14" - 36"
9"
36" - 60"
15"
50" - 76"
19"
field (objects in focus) will also change and will also require operator
adjustment. For that reason, zoom lenses are generally not suitable for
near real time alarm assessment purposes. Automated devices, called "shot
boxes," are available which will automatically return a zoom lens to a
particular setting when not under operator control or upon alarm in the zone
covered by the camera. This should be the only acceptable method for the
system designer to apply a zoom lens camera as an alarm assessment camera.
Since zoom lenses cost two to 10 times more than fixed focal length lenses
and the shot box is also an added cost, careful cost-effectiveness analyses
should be completed prior to selection of a zoom lens option for alarm
assessment.
6.2.4.2 Tilt and Pan. Tilt is the movement of a platform up and down. Pan
is side-to-side movement (see Figure 33). Tilt and pan CCTV camera mount
13.02-92
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