ColorMatrix + large images == no love

programming flash
1

Hi all
I have been using a fairly standard colour matrix but have found it does not work at all if my image exceeds the stage size.
I am trying to apply this effect to a jpg that is 900x1600px but to no avail.
any pointers would be much apriciated

function loaded(event:Event):void {
	var targetLoader:Loader = Loader(event.target.loader);
	Bitmap(targetLoader.content).smoothing = true;
	swapChildren( bck, container );
	bck.addChild(targetLoader);
	cma = new ColorMatrix();
	cma.adjustColor(100, 100, 0, 0);
	bck.filters = [new ColorMatrixFilter(cma)];
	targetLoader.x = 0;
	targetLoader.y = -100;

            var minuteTimer:Timer = new Timer(1, 20);
            _brightness	=100;
		_saturation	= 100;
            minuteTimer.addEventListener(TimerEvent.TIMER, onTick);
            minuteTimer.start();
       

     function onTick(event:TimerEvent):void 
        {
	_brightness -=5;
	_saturation -=5;	
	cm = new ColorMatrix();
	cm.adjustColor(_brightness, _saturation, 0, 0);
	bck.filters = [new ColorMatrixFilter(cm)];
           
			if(_brightness <= 0){
				LOADMENU();
			}
			
        }
}