Axis IP-Surveillance system Design Manual page 28

> Secure support
A camera should be placed on stable supports to minimize camera movement. As PTZ cameras move
around, the action can cause image interference if the camera mounting is not properly secured. In
outdoor situations, sturdy mounting equipment should always be used to avoid vibrations caused by
strong winds.
> Use lots of light/Add light if needed
The most common reason for poor quality images is lack of
light. Generally, the more light, the better the images. With
too little light, the images will become blurred and dull in
color. You can easily and cost-effectively add strong lamps in
both indoor and outdoor situations to give you the light
conditions necessary for capturing good images.
Lux is the standard unit of measurement for light. The table at right shows the available light in
different kinds of conditions. At least 200 lux is needed to capture good quality images. A high-
quality camera might be specified to work down to 1 lux, which means that you can capture an image
at 1 lux, but it may not be of high quality. Different manufacturers use different references when they
specify the light sensitivity of a camera, and this makes it difficult to compare cameras without first
testing them and comparing the images captured.
When using external, artificial lighting in outdoor environments, reflections and/or shadows should
be avoided.
For covert security or in areas where the presence of artificial light is unwanted, you can choose to
use an IR-sensitive, black and white camera, or an automatic, day/night camera. In a day/night
camera, color video is delivered during light conditions, while at night, the camera makes use of
near-infrared light to generate IR-sensitive, black and white video. An IR illuminator, which provides
infrared light, can also be used in conjunction with an IR-camera or a day/night camera to further
enhance a camera's ability to produce high-quality video in low-light or nighttime conditions.
Figure 3.d. IR-sensitive network camera with IR illuminator attached below the camera housing
Environment: lux
> Strong sunlight: 100,000
> Full daylight: 10,000
> Normal office light: 500
> Poorly lit room: 100
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