Lorex Guide to Security Camera Field of View (FOV)
One of the most important considerations when choosing security cameras for your home or business is how much area you need to monitor. The best way to determine which camera will capture the full area you are interested in monitoring is to look for the camera's field of view. This article addresses the pros and cons of both wide and narrow angle lenses, and will help you make more informed decisions when choosing which camera is the best one for the job.
The field of view of a security camera, also called the viewing angle, is the area that the camera can see. On a specification sheet, you will see the field of view measured in degrees. Think of the field of view as the angle between the two horizontal edges of the camera image. Check out the following examples to see this principle at play:
The 60° field of view captures some of the objects but in greater detail
The 90° field of view captures all of the objects but in lesser detail
As you can see in the example images above, the camera with 90° field of view captures all 3 objects in the scene, though each object takes up a small part of the camera image. The camera with 60° field of view captures some of the objects but in greater detail.
Remember, a wider field of view isn?t always better! There are pros and cons to each scenario – click here to learn more about how lens size affects field of view and what type of lens you should look for when choosing a security camera.
Smaller lenses are known as wide-angle lenses, which produce a greater field of view than cameras with a larger lens. They capture a large area, though objects will appear smaller within the camera image. Wide-angle lenses are designed for monitoring large areas, such as:
Back or Front Yards
Larger lenses, or narrow-angle lenses, have a smaller field of view. They capture a limited area, but objects will appear larger and more detailed within the camera image. Narrow-angle lenses are designed for monitoring a specific target, such as:
Doorways and Entrances
Objects of Value
The size of the camera lens, or focal length, is the main factor that determines the field of view. The example images compare multiple focal lengths and the resulting fields of view:
Focal length: 3.6mm
Field of view: 78°
Focal length: 5.1mm
Field of view: 58°
Focal length: 6mm
Field of view: 51°
Focal length: 9mm
Field of view: 39°
A fixed lens is one where the camera?s focal length is permanently set and cannot be adjusted by the user. This means that the field of view is permanently set, so it is important to select the correct field of view (i.e., wide- or narrow-angle) for your application.
A varifocal lens allows the user to manually adjust the camera lens, generally using adjustment screws or knobs. Varifocal cameras are typically more expensive than the equivalent fixed lens model, but they allow for greater flexibility to optimize the camera picture for your specific needs. The focus settings on a camera with a varifocal lens may need to be adjusted from time to time.
If your application demands you to quickly switch between a narrow and wide field of view, we?ve got a solution for that too! Consider buying a PTZ camera – they have a motorized varifocal lens that can be used to change the field of view from your DVR, NVR or a connected smartphone or tablet. PTZ cameras have other advanced features making them the most expensive type of camera, so they are only recommended for the most demanding applications.