Roman - You need to learn about DORI. This is the distances that you can use a camera to "Detect" the presence of someone, "Observe" what they are doing, "Recognize" someone you know, and "Identify" a stranger. These numbers vary based on the camera's resolution and focal length. Good manufactures will print the DORI distances in the spec sheet of each camera model.
Long story short, a person typically has to be very close to a camera (generally within 15-25') to be able to identify a stranger. If that person walks 20 yards away from the camera, you will be lucky if you can "observe" what they are doing. The only way to be able to "identify" a person that far away is to zoom in on them This means using either a single purpose camera with a lot of zoom capability pointed at a specific "target of interest" (ie an access gate, etc), or a PTZ camera that you can move and control. Just keep in mind that PTZ cameras are not the "do everything/perfect" solution either. They work well when someone is monitoring them 24/7, but are less effective when they are not monitored because they tend to be pointed in the wrong direction when something of interest happens. Unless you can find a camera with tremendous resolution (MUCH more than 8k), there is no way you can get both a "wide view" and enough clarity to identify people 50-100' away.
Just keep that in mind when you start planning on where you want to put cameras and what you expect to be able to capture with them.
