These Security Cameras offer a Varifocal Lens. Varifocal lenses offer the ability to manually adjust the camera lens to get a desired field of view. This simply lets you zoom in out out to adjust the camera to the picture you want. Cameras that offer varifocal lenses come with predetermined focal lens sizes. As an example you may have a camera with a 2.8mm-12mm lens. This means that you can adjust the camera from a 2.8mm wide angle view all the way up to a 12mm view wich is closer and narrower.