Determine how many security cameras you need to cover your property.
Camera coverage is trigonometry. A camera sees a triangle, and the width it covers at a given distance is twice that distance times the tangent of half the field of view — a 110 degree lens covers about 114 ft across at 40 ft out. Divide the perimeter you care about by that width and you have the perimeter camera count. Then add one camera per entry door, because the perimeter view identifies that someone is there while the door camera identifies who, and one for the driveway if vehicles and plates matter. The range figure to use is identification range, not the night-vision distance on the box: a 4 MP camera resolves a recognisable face to roughly 30-45 ft and beyond that records a person-shaped blur.
Home Security Camera Coverage
Coverage width = 2 x range x tan(field of view / 2); perimeter cameras = perimeter / coverage width; total = perimeter cameras + doors + driveway
Camera placement can have legal implications. Recording beyond your property boundary, covering a neighbour's windows or capturing audio may breach privacy or data protection law in your jurisdiction — check local rules before installing.
Not for identification. A 180 degree lens covers more ground but spreads the same pixels over it, so faces become unusable much closer in. Wide lenses are for situational awareness, narrow ones for recognising people.
Motion-triggered recording cuts storage by 70-80% but misses the seconds before the trigger unless the camera has pre-buffer. Continuous recording on the two most important cameras and motion on the rest is a common compromise.