Camera is zooming way far out

[SerializeField]
private Transform target;
[SerializeField]
private float rotationSpeed = 10f;

[SerializeField]
private float bobPeriod = 2f;
[SerializeField]
private float bobAmplitude = 2f;

private float startY;
private float bobDistance;

// Use this for initialization
void Start () {

    //store the start position of the camera
    startY = transform.localPosition.y;

}

// Update is called once per frame
void Update () {

    //update the vertical camera bob
    bobDistance = Mathf.Sin(Time.timeSinceLevelLoad / bobPeriod) * bobAmplitude;

    transform.position = new Vector3 (transform.localPosition.x, startY + bobDistance, transform.localPosition.z);

    //update camera position
    transform.RotateAround (target.position, Vector3.up, rotationSpeed * Time.deltaTime);

    //update the camera look
    transform.LookAt (target);

}