Can not access dual camera at Iphone 7+

Hi, I tried to access the Iphone 7+ dual camera. First I try to access the camera devices from WebCamDevice.

  private WebCamDevice[] devices;
  void Start()
     {
         devices = WebCamTexture.devices;
         WebCameraCnts = devices.Length;
         for( int i = 0 ; i < devices.Length ; i++ )
             Debug.Log(devices[i].name);   
 }

Then I build the apps to Iphone7+ and watch the log from XCode. But the output is only: Back Camera,

Front Camera

and there is no another camera. (supposed there should be 3 cameras at Iphone 7+?) Does anyone know how to access the dual camera at Iphone 7+? Thanks.