Problem with Camera

im making a sidescroller game, so i need a camera that fallows the player as he moves, i got this code:

import flash.geom.Matrix;
import flash.geom.Transform;
import flash.geom.ColorTransform;
var copyrightNotice = “Copyright © 2006-2007 Sockpuppet Pty Ltd. All Rights Reserved. http://www.reanimator.net”;
var reanimator = new Transform(this);
var camera = new Transform(this._parent);
var w:Number = Stage.width;
var h:Number = Stage.height;
this._visible = false;
this.onEnterFrame = function () {
this._parent.filters = this.filters;
var stageMatrix:Matrix = reanimator.matrix;
camera.colorTransform = reanimator.colorTransform;
stageMatrix.invert();
stageMatrix.translate(w*.5, h*.5);
camera.matrix = stageMatrix;
}

your stupposed to put that one inside a mc on the frame, and then you put this code:

onClipEvent (enterFrame) {
_x += (_root.player._x-_x)/4;
}

on the outside on top of mc.

the problem is that the camera is off, it cuts off about 3/4s of my original stage. cam anybody help?