$(document).ready(function(){
  // Add the hover handler to the link
  $(".img_hover_trans").hover(
    function(){ // When mouse pointer is above the link
      // Make the image inside link to be transparent
      $(this).find("img").animate(
        {opacity:"0.5"},
        {duration:300}
      );
    },
    function(){ // When mouse pointer move out of the link
      // Return image to its previous state
      $(this).find("img").animate(
        {opacity:"1"},
        {duration:300}
      );
    }
  );
});

$(document).ready(function(){
  // Add the click handler to the link
  $("ul.portfolio_list li , ul.privat_list li").click(function(){ 
      $("img.attachment-featured-small").animate(
        {opacity:"0.1"},
        {duration:300}
      );
    },
    function(){ // When mouse pointer move out of the link
      // Return image to its previous state
      $(this).find("img").animate(
        {opacity:"1"},
        {duration:300}
      );
    }
  );
});