Efecto de iluminación en imágenes al pasar el mouse

<script language="javascript" type="text/javascript">
nereidFadeObjects = new Object();
nereidFadeTimers = new Object();
function nereidFade(object, destOp, rate, delta){
if (!document.all)
return
if (object != "[object]"){ //do this so I can take a string too
setTimeout("nereidFade("+object+","+destOp+","+rate+","+delta+")",0);
return;
}

clearTimeout(nereidFadeTimers[object.sourceIndex]);

diff = destOp-object.filters.alpha.opacity;
direction = 2;
if (object.filters.alpha.opacity > destOp){
direction = -2;
}
delta=Math.min(direction*diff,delta);
object.filters.alpha.opacity+=direction*delta;

if (object.filters.alpha.opacity != destOp){
nereidFadeObjects[object.sourceIndex]=object;
nereidFadeTimers[object.sourceIndex]=setTimeout("nereidFade(nereidFadeObjects["+object.sourceIndex+"],"+destOp+","+rate+","+delta+")",rate);
}
}
</script>