Camera Zoom for Orthographic (iPhone Touch)

Im hoping someone can help me with this. I have a Orthographic camera and I would like to be able to zoom in and out with touch controls.

I've been using a script for CameraZoomPinch which works great for a Perspective Camera but I cant seem to modify it correctly for an Orthographic Camera.

A Perspective camera uses fieldOfView to zoom and a Orthographic camera uses size to zoom

 using UnityEngine; using System.Collections;
 
 public class CameraZoomPinch : MonoBehaviour 
 {
     public int speed = 4;
     public Camera selectedCamera;
     public float MINSCALE = 2.0F;
     public float MAXSCALE = 5.0F;
     public float minPinchSpeed = 5.0F;
     public float varianceInDistances = 5.0F;
     private float touchDelta = 0.0F;
     private Vector2 prevDist = new Vector2(0,0);
     private Vector2 curDist = new Vector2(0,0);
     private float speedTouch0 = 0.0F;
     private float speedTouch1 = 0.0F;
 
     // Use this for initialization
     void Start () 
     {
 
     }
 
     // Update is called once per frame
     void Update () 
     {
 
        if (Input.touchCount == 2 && Input.GetTouch(0).phase == TouchPhase.Moved && Input.GetTouch(1).phase == TouchPhase.Moved) 
        {
 
          curDist = Input.GetTouch(0).position - Input.GetTouch(1).position; //current distance between finger touches
          prevDist = ((Input.GetTouch(0).position - Input.GetTouch(0).deltaPosition) - (Input.GetTouch(1).position - Input.GetTouch(1).deltaPosition)); //difference in previous locations using delta positions
          touchDelta = curDist.magnitude - prevDist.magnitude;
          speedTouch0 = Input.GetTouch(0).deltaPosition.magnitude / Input.GetTouch(0).deltaTime;
          speedTouch1 = Input.GetTouch(1).deltaPosition.magnitude / Input.GetTouch(1).deltaTime;
 
 
          if ((touchDelta + varianceInDistances <= 1) && (speedTouch0 > minPinchSpeed) && (speedTouch1 > minPinchSpeed))
          {
 
           selectedCamera.size/*fieldOfView*/ = Mathf.Clamp(selectedCamera.size/*fieldOfView*/ + (1 * speed),15,90);
          }
 
          if ((touchDelta +varianceInDistances > 1) && (speedTouch0 > minPinchSpeed) && (speedTouch1 > minPinchSpeed))
          {
 
           selectedCamera.size/*fieldOfView*/ = Mathf.Clamp(selectedCamera.size/*fieldOfView*/ - (1 * speed),15,90);
          }
 
        }     
     }
 
 }

If I change fieldOfView to size I get an error:

UnityEngine.Camera' does not contain a definition for size' and no extension method size' of type `UnityEngine.Camera' could be found (are you missing a using directive or an assembly reference?)

puzzling I could be wrong but I thought the Orthographic camera has a size variable