UFC 4-021-02NF
27 September 2006
change 1, 23 October 2006
4-6.2.4
To be mounted in a position to prevent glare to the lens from overhead
lighting.
4-6.2.5 Manual adjustment that the operator at the monitor station can use to
accommodate backlighting situations caused in situations such as when a camera
faces a door to the outside with too much light coming to the camera lens, causing a
backlight situation.
4-6.3
Outdoor Cameras. Outdoor camera installations cost more than indoor
cameras due to the need to environmentally house, heat, and ventilate the outside
camera. When mounting a camera outdoors, the lighting requirement changes
depending on the time of day and the weather. Because of this, consider the following
for outdoor cameras:
4-6.3.1 Shrubs, trees, and other vegetation in a camera's line of sight may cause
obstructed views. Designers need to be aware of this when determining where to place
cameras. Also, motion detector systems can register a false positive when plants in the
field-of-view move in windy conditions.
4-6.3.2
Provide heaters in cold weather applications.
4-6.3.3 Always use auto-iris lenses with outdoor cameras. The iris automatically
adjusts the amount of light reaching the camera and thereby optimizes its performance.
The iris also protects the image sensor from getting damaged by strong sunlight.
Always set the focus in low light with an auto-iris lens. If the adjustment is made in
sunlight, it is very easy to focus, but at night the iris diameter increases and the image is
not in focus anymore. Special dark focus filters called "neutral density" filters or ND
filters help reduce lighting by one or more stops of exposure. These filters do not affect
the color of the image.
4-6.3.4 Use caution when mounting a camera behind glass. If you mount a camera
behind glass, such as in a housing, make sure that the lens is close to the glass. If the
lens is too far away from the glass, reflections from the camera and the background will
appear in the image.
4-6.3.5 Always try to avoid direct sunlight in an image. Direct sunlight blinds the
camera and may permanently bleach the small color filters on the sensor chip, causing
stripes in the image. If possible, position the camera so that it is looking in the same
direction as the sun.
4-6.3.6 When using a camera outdoors, avoid viewing too much sky. Due to the large
contrast, the camera will adjust to achieve a good light level for the sky, and the
landscape and objects that must be assessed might appear too dark. One way to avoid
these problems is to mount the camera high above ground. Use a pole if needed. Given
mounting choices, mount cameras facing away from rising or setting sun, realizing that
this varies by season.
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