Security Camera Mysteries: What is Angular Field of View?

Anybody who's considering adding a first-rate video surveillance system (consisting of security cameras and some form of monitoring and recording equipment, at minimum) needs to know a few things before committing any money to one. For one, understanding how widely the camera can "see" is important, because buying a camera that can only see in very narrow ranges means one is buying a camera that under-performs.

This is where knowing what the camera's angular field of view comes in.

In cameras, "field of view" is sometimes abbreviated as FOV and anything outside of the camera's field of view isn't able to be recorded as an image by the camera.

In effect, it's that part of the world that that can be seen through the camera at any given position of the camera and at any orientation (up, down, sideways etc.) in space.

However – and this is important – a camera's FOV isn't exactly the same as the camera's angular field of view, which is normally abbreviated as AOV.

And though the terms are often used in a kind of interchangeable way, the difference is in how each is measured.

For FOV, the standard of measurement involves feet, inches and the like. AOV in degrees of an arc (10 degrees, 20 degrees etc.).

Basically, a security camera's AOV means the field of view of the camera when it pointed in any direction space and amount of view that'll be present.

If a camera has a 15 degree down angle – like what one might see in a camera sitting on the top of a corner of a building – it will be able to see  certain things that a camera pointed downwards at a 30 degree AOV can't and vice versa.

Perhaps it's easier to understand by imaging a horizon line.

A camera pointed at zero degrees of arc will be looking straight-on at the line and will be able to see equal degrees of arc above and below the line.

Point the camera downwards by 5 degrees, though, and less of the field above the line will be seen but more of the field below the line will also be viewable. It's a kind of trade-off.

Normally, an effective AOV or angular field of view for a security camera depends on the size of the area a camera must keep under surveillance.

This depends on the height of the camera as well. If it's up high, 15 to 30 downward degrees of arc may be best. If it's down low but must be able to see a wide area, then an upwards arc of from 15 to 25 degrees might work.

Most people who are working with their system installers should try to get a look at what the camera is imaging and what the area being visualized by the camera looks like at various angles and then make a determination from there.

Always make sure the camera is able to sweep upwards and downwards or that it can see a wide area both above and below the horizon line in order to obtain cameras that can keep under surveillance enough of the area that needs to be secured.