A cameras lens size determines the field of view, a lower lens size equates to a wider angle view, most cameras have a fixed lens size.
For installations using fixed lens cameras, we recommend a 2.8mm (103° view angle) to 4mm (80° view angle ) lens.
Varifocal Lens cameras, are ones where the focal length can be altered and can be set to a wide or very narrow angle. For example, you may want to cover a gate 20m from the camera, this would need to be set to a narrow setting (around 10 to 12mm). The typical range of a varifocal lens cameras is 2.8 to 12mm.
Varifocal cameras can be manual zoom, where the focal length is adjusted (usually via settings on base of the camera) at the time of installation, or motorized lens, which as the name implies, has a built in motor to adjust the focal length. The adjustment can be made from the recorder and even remotely via a smartphone.