field of view isn't how you should look at it.
its what you want the camera to do that's important.
1. see someone? field of view is essential
2. identify someone? quality of what you can see is important, ie face at a resolution of 250 minimum pixels per meter camera too high up and the angle of the camera is too much then you are going to get tops of heads. lower down you have to be aware that access to the camera is easier.
Had a sparky talk to one of my clients this week just gone advising them the cameras were installed too low down and could be tampered with, the height he wanted to put them at would have been useless for ID, the customer is aware of that. when the cameras were placed and at the demo they were placed as high as they could be due to obstructions but still able to give good clear facial recognition and cover as larger area as possible, hence why the cameras are antivandal, but they could be sprayed over but they would have to be close and by at least 6ft tall with a reach of a few feet plus spray distance on many and two of the cameras are a little lower due to obstructions, making them lower down but due to the obstructions the intruder would have to be close to spray the lens.
That said they would have been picked up at different locations by one or more other cameras by the time they reached one to spray it as coverage is set up that way, unless they have a spray can on a really long pole.
What the customer has noticed is that some people, ie some of the window cleaners try and hide there face when they visit the property, makes you wonder what they have to hide?