Field of View

A consideration to take into account when selecting a camera is the field of view required; that is, the area of coverage and the degree of detail to be viewed. The field of view is determined by the focal length of the lens and the size of the image sensor; both are specified in a camera’s datasheet.

A lens’ focal length is defined as the distance between the entrance lens (or a specific point in a complicated lens assembly) and the point where all the light rays converge to a point (normally the camera’s image sensor). The longer the focal length, the narrower the field of view.

Field of View Calculator

Which lens is the best fit for your particular needs? Use the calculator below to determine the “mm” rating of the lens required. Enter the distance from camera to object to monitor AND the height or width of the area camera will monitor.

The field of view can be classified into three types:
Normal view: offering the same field of view as the human eye.
Telephoto: a narrower field of view, providing, in general, finer details than a human eye can deliver. A telephoto lens is used when the surveillance object is either small or located far away from the camera. A telephoto lens generally has less light gathering capability than a normal lens.
Wide angle: a larger field of view with less detail than in normal view. A wide-angle lens generally provides good depth of field and fair, low-light performance. Wide-angle lenses sometimes produce geometrical distortions such as the “fish-eye” effect.

1 – Lens format: 1/4″
2 – Distance to object (feet):  
3 – Width of picture (feet):  
3 – Height of picture (feet):  
4 – Lens focal length (mm):  

Example: You are installing a camera to monitor a main entry door. Camera will be placed to the side of the door. You want to know the “mm” rating of the lens required to achieve ideal coverage.
“1 – Lens format: 1/3” = this is the most common lens format
“2 – Distance to object (feet):” = in our example “distance to object” means distance to person; let’s say 5ft away from the door
“3 – Width of picture (feet):” = skip this step for our example as it is easier to enter the height of a person
“3 – Height of picture (feet):” = in our example “height of picture” means height of person; let’s say this person is 6ft tall
Click “Calculate” button; in our example you will receive a recommended value of “3mm.” This means a camera with a 2.8mm lens is ideal.