UFC 4-021-02NF
27 September 2006
change 1, 23 October 2006
drywall. For retrofit projects, the same modeling approach can be applied, but requires
changing existing surfaces or modifying lighting sources and locations.
4-10
VIEWING IN LOW-LIGHT CONDITIONS
4-10.1
In addition to increasing the illumination level of the surrounding area, several
technology solutions are available to permit viewing under low-light conditions. These
include black/white switching cameras, infrared illuminators, or thermal imagers. These
technologies are often used where visible light either brings undesired attention to a
critical facility, or surrounding property owners object to visible light adequate for good
visual camera operation.
4-10.2
Black/White Switching. Some cameras will automatically switch from color
during daytime to black/white at night, which permits viewing under low light conditions.
This can be an effective solution in situations where the existing illumination levels are
too low during night conditions to permit color camera use, but color camera use is
desired during daytime conditions. Numerous CCTV camera manufacturers offer auto-
switching black/white cameras.
4-10.3
Infrared Illuminators. The human eye cannot see infrared light. Most
monochrome CCTV (black/white) cameras, however, can. Thus, invisible infrared light
can be used to illuminate a scene, which allows night surveillance without the need for
additional artificial lighting. Infrared also provides many other benefits above
conventional lighting, including:
4-10.3.1 IR beam-shapes can be designed to optimize CCTV camera performance
4-10.3.2 Extended bulb-life
4-10.3.3 Covert surveillance, no visible lighting to alert or annoy neighbors
4-10.3.4 Lower running costs (but higher installation costs)
4-10.3.5 Ranges at which illuminators are effective vary with manufacturer and model.
Typical values are 10 meters to 85 meters.
4-10.3.5.1 It is important to design illumination specifically for the CCTV camera being
used. For example, infrared illuminators require black/white cameras and do not work
on color cameras. The range that the camera will see in the dark depends on sensitivity
and spectral response of the camera and lens combination. Color cameras will not
accurately reproduce color images when used under infrared illumination. Many black
and white cameras use infrared filters to intentionally filter out non-visible light.
Therefore, black and white cameras which are designed to be used in conjunction with
infrared lighting should be specified such that there is not infrared filter. Dual mode
cameras that can switch from color to monochrome operation in low light conditions
should also have any infrared filter removed for the reason cited above.
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