Top ten installation challenges
When planning camera placement during installation, many factors must be taken into account. As mentioned in Camera Selection, the surveillance objectives will determine what type of camera should be used, as well as how it should be positioned.
Getting a useful image involves much more than simply pointing the camera in the required direction. Lighting (and backlighting), angles, reflections, dead zones, and the zoom factor for PTZ cameras are all matters to consider. Sometimes, it’s actually easier to change the environment itself, for example by shading windows or moving objects to new locations.
Camera placement is also an important factor in deterring vandalism. By placing a camera out of reach on high walls or on the ceiling, many spur-of-the-moment attacks can be prevented. The downside may be that the angle of view is affected, which can be compensated for to some extent by selecting a different lens.
The purpose of each camera should be clearly specified. If the aim is to get an overview of an area, to track the movement of people or objects, make sure that a camera suitable for the task is placed in a position that can achieve the objective.
If the intention is to identify persons or objects, the camera must be positioned or focused in such a way that it captures the required level of detail. Local police authorities may be able to provide guidelines on how best to position a camera.
Field of view
The fastest way to find the focal length of the lens required for a desired field of view is to use Axis online lens calculator.
The distance from the camera to the object
To calculate the distance from camera to subject, use Pythagorus’ Theorem: a² + b² = c²
Large area coverage with capture points
Although a single camera will provide an overall view of a scene, it might not provide enough detail to identify individuals. If this is one of the surveillance goals, then an additional camera can be included in the design (see below). Identification is now possible as a person enters the area.
Lighting considerations are crucial to successful camera placement. It is normally simple and cost-effective to add extra lighting to create the necessary conditions for getting good images, in both indoor and outdoor situations.
When mounting cameras outdoors, it is important to consider how the light will change during the day. It is also important to avoid direct sunlight, as this will blind the camera and possibly reduce the performance of the image sensor. If possible, position the camera so that the sun is behind it.
Backlight problems typically occur when attempting to capture an object in front of a window. Try repositioning the camera, or possibly block some of the light. If repositioning the camera is not an option, add some frontal lighting instead. Cameras with support for wide dynamic range are better at handling backlit scenarios.
Direction of the sun
When mounting cameras outdoors, it is important to consider how the light will change during the day. Towards the end of the day, the camera in the red circle in Figure 12 would be facing the sun.
If the exterior of a building is to be monitored, the location can be more or less affected by direct sunlight. Place the camera where sunlight has the minimum impact.
The different ranges/zones of a camera are depicted in the figures below. The line closest to the camera in Figure 13 is where the maximum height is detectable. The yellow line illustrates the minimum required detectable height. The detection zone is in between these lines. These factors need to be addressed at the time of installation, to ensure proper camera coverage.
Field of view must be checked both horizontally and vertically. If using floor plans, remember that these will only give you a birds-eye view of the area. The side view must also be considered, to ensure the required coverage.
Camera to object angle
When placing a cameras by a door or in a lobby, care should be taken to avoid placement at too high an angle. As seen here, the greater the angle, the more difficult it is to see facial features. In our example, an angle of 10-15° gives the best view for facial identification. On the other hand, placing a camera higher up puts it out of reach for vandals. It all comes back to the surveillance goals – is identification required or is an overview sufficient?