QuickFOV

function QuickFOV(){
//If you don't have an animated zoom, you can use this function to quickly calculate your FOV from Maya.
var pi = Math.PI;
var aspect = scene.defaultResolutionX() / scene.defaultResolutionY();

d = new Dialog;
    d.title = "Paste Focal Length and Horizontal Film Aperture.";
var focalLength = new LineEdit;
var camAp = new LineEdit;
 focalLength.label = "Focal Length";
    focalLength.text = "";
    camAp.label = "Horizontal Film Aperture";
    camAp.text = "";
 var group = new GroupBox;
  group.add(focalLength);
   group.add(camAp);
   d.add(group);
   rc = d.exec();
   if (!rc){
       return;
   }


function FOV(CamAp, FocLen){
    var CamApMM = CamAp * 25.4; //converts inches to mm
    var CamApVert = CamApMM / aspect;
    var xrad = (Math.atan((CamApVert/2) / FocLen)) * 2;
    var AngleOfView = xrad*180/pi;
    return AngleOfView;
};
MessageBox.information("Your FOV value is " + FOV(parseFloat(camAp.text), parseFloat(focalLength.text)));
}