Except the effect in previous example to zoom in and out on hovering the graphics, I have added an opacity level changed on each. Only need to add a class name imghover and add the script below.

Function: fadeTo(speed, opacity, callback) - Fades the opacity of all matched elements to a specified opacity and fires an optional call back after completion.

 
<script type="text/javascript">
    $(function() {
    $(".imghover").hover(
      function() {             
        $(this).fadeTo("fast", 0.7);
      },
      function() {             
        $(this).fadeTo("fast", 1.0);
      });
    });
</script>