How can I identify width of camera vision?

[Des]

I purchased any old IP POE Turret camera and placed it above my front door. It captures the face of visitors well and most of my car but I can only see my wifes car wheels parked next to mine.

How can I go about assessing what the spread of vision will be for any given camera at any given distance? Is there a formula I can use? How is this information presented on an IP camera for sale so I can identify specification.

I imagine it will be something that says width of vision is 3X for every X distance from camera lens but Im not sure?

 

[Phil]

IP cameras often don't reveal within their user interface what lens you have.
i.e. when checking the settings they look the same whether you have a 2.8, 4, 6, 12mm camera.
The software simply does not know/show what lens was fitted in the factory.

However, normally, it will say 4mm or whatever on the label on the product, or on the box it came in.
The lower the number for focal length, the wider the field of view - so 2.8mm provides a wider field of view than 4mm.
On most of our camera product pages in the webshop we will state and illustrate the field of view you will achieve with a given lens (it's a factor of the lens focal length and the sensor chip size, so does vary between cameras).

For a door camera we'd normally recommend a 2.8mm lens.
Typically the widest you can get for most cameras.
Because people will be close to the camera, so identification is not a big challenge, and if you use a narrower field of view it is all too easy for people to be out of view simply by standing to either side of the door.

We use software to do lens calcs / provide illustrations.

You should be able to find similar on the web.