change source image but not now! ;p

change source image but not now! ;p

in function :

                 $("#bigfoto").animate({left: '+=150px'},300);
       $("#bigfoto").fadeOut(400);
       $("#bigfoto").attr("src","p/kol.png");
       $("#bigfoto").fadeIn(400);
       $("#bigfoto").animate({left: '-=150px'},300);


why this code is executed at the beginning ?
I wont change source when opacity #bigfoto is set to 0!!
any ideas?
$("#duzefoto").attr("src","p/kol.png");