$(document).ready(function(){
  $(".photo-list img").mouseover(function() {
      $(this).fadeTo(150, 0.4);  
      $(".lightbox").addClass("click-for-enlarge");
  });
  $(".photo-list img").mouseout(function() {
      $(this).fadeTo(150, 1);  
  });  
  
    $(".portfolio-list img").mouseover(function() {
      $(this).fadeTo(150, 0.4);  
  });
  $(".portfolio-list img").mouseout(function() {
      $(this).fadeTo(150, 1);  
  });  
 
});