Your comments about fisheye lenses make sense but don't explain why a reputable maker like Hikvision who recently introduced the second generation of their video intercom system opted to fit a 2MP fisheye lens to the gate station. I'm assuming that this gives some leeway if visitors are very close to the camera but not directly in front of it but i would imagine a wide FOV conventional lens could offer that flexibility. So why do you think they went for fisheye?
Hi Kay, I think you are right that they have chosen a fisheye lens for as much coverage as possible in small areas. it works in this scenario better than a fixed 2.8/4mm lens because the intercom camera is not designed for surveillance and instead are just designed for observing that area directly around the door/gate the intercom is connected to. The intercom is designed to be used in conjunction with other cameras and not just as a single camera solution.
