CameraZoom

using UnityEngine;
using System.Collections;

[AddComponentMenu("Camera/Camera Zoom")]

public class CameraZoom : MonoBehaviour {

    public LayerMask layersToCollide;
    public float smooth = 18;

    private Transform cameraPivot;
    private CameraFollow cameraFollow;
    private RaycastHit hit;
    private Vector3 defaultPos;
    private float startDistance;

    void Start () {
        cameraFollow = GetComponent <CameraFollow> ();
        cameraPivot = GameObject.Find ("CameraPivot").transform;

        defaultPos = new Vector3 (0, cameraFollow.height, - cameraFollow.distance);

        startDistance = cameraFollow.distance;
    }

    void LateUpdate () {
        //Draw line on editor screen
        Debug.DrawLine (cameraPivot.position, cameraPivot.TransformPoint(defaultPos), Color.black);

        //Create bool true if there something between player and camera
        bool isColliding = Physics.Linecast (cameraPivot.position,
                                             cameraPivot.TransformPoint (defaultPos),
                                             out hit,
                                             layersToCollide);

        //Change camera distance if there's something between player and camera
        if (isColliding && hit.distance < startDistance)
            cameraFollow.distance = Mathf.MoveTowards (cameraFollow.distance,
                                                       hit.distance,
                                                       smooth * Time.deltaTime);
        else
            cameraFollow.distance = Mathf.MoveTowards (cameraFollow.distance,
                                                       startDistance,
                                                       smooth * Time.deltaTime);

    }
}