제이쿼리 fadein을 이용한 효과 입니다.
1번 이미지 위에 2번 이미지가 출력 됨으로 서서히 생기는 착시 효과가 발생합니다.



  <div id="wrap">

    <div id="main_img_img" class="main_visual" style="position:absolute;z-index:10;top:0px;left:0;width:100%;">
            <div class="main_visual_img"><img src="images/common/main_img_1.jpg" alt=""></div>
        </div>
    <div id="main_img_img2" class="main_visual" style="position:absolute;z-index:11;top:0px;left:0;width:100%;display:none;">
            <div class="main_visual_img"><img src="images/common/main_img_2.jpg" alt=""></div>
        </div>
    <div id="main_img_img3" class="main_visual" style="position:absolute;z-index:12;top:0px;left:0;width:100%;display:none;">
            <div class="main_visual_img"><img src="images/common/main_img_3.jpg" alt=""></div>
        </div>

</div>

  <script type="text/javascript">
  //<![CDATA[

  var s = null;
  var img_arr = new Array();
  img_arr[0] = "images/common/main_img_1.jpg";
  img_arr[1] = "images/common/main_img_2.jpg";
  img_arr[2] = "images/common/main_img_3.jpg";

  var i = 0;
  function TiVis(){
    clearInterval(s);

            i++;
            if(i==3) {
                i=0;
             }

            if( i == 0 ){ $("#main_img_img").css({zIndex : 13});$("#main_img_img2").hide(); $("#main_img_img").fadeIn(1000);}
            if( i == 1 ){ $("#main_img_img").css({zIndex : 10});$("#main_img_img").hide();$("#main_img_img3").hide(); $("#main_img_img2").fadeIn(1000);}
            if( i == 2 ) $("#main_img_img3").fadeIn(1000);

        s = setInterval( "TiVis()", 4000 );
    }
  s = setInterval( "TiVis()", 4000 );
function delay(gap){
  var then,now;
  then=new Date().getTime();
  now=then;
  while((now-then)<gap){
  now=new Date().getTime();
  }
}
function ICallBack( j ){
      $("#main_img_img img").attr( 'src', img_arr[j] );
}
  //]]>
  </script>