Carousel transition entre images

Bonjour,

dans mon carousel, j'aimerais que la transition se fasse plus lente et plus opaque d'une image à une autre.

Sauriez vous ce qu'il faut code et où s'il vous plait ?
jE VOUS REMERCIE.

Voici mon code actuel au cas ou :

/*
    CARROUSEL JS
*/


var carrousel = {
    
    nbSlide : 0,
    nbCurrent : 1,
    elemCurrent : null,
    elem : null,
    timer : null,
    
    init : function(elem){
        this.nbSlide = elem.find(".slide").length;
        
        // Créer la pagination
        elem.append('<div class="navigation"></div>');
        for(var i=1;i<=this.nbSlide;i++){
            elem.find(".navigation").append("<span>"+i+"</span>");
        }
        elem.find(".navigation span").click(function(){ carrousel.gotoSlide($(this).text()); })
        
        // Initialisation du carrousel
        this.elem=elem;
        elem.find(".slide").hide();
        elem.find(".slide:first").show();
        this.elemCurrent = elem.find(".slide:first");
        this.elem.find(".navigation").css("opacity",0.6);   // On rend la navigation opaque
        this.elem.find(".navigation span:first").addClass("active");
        
        // On cré le timer
        carrousel.play();
        // Stop quand on passe dessus
        elem.mouseover(carrousel.stop);
        elem.mouseout(carrousel.play);
    },
    
    gotoSlide : function(num){
        if(num==this.nbCurrent){ return false; }
        
        /* Animation en fadeIn/fadeOut 
        this.elemCurrent.fadeOut();
        this.elem.find("#slide"+num).fadeIn();
        */
        /* Animation en slide 
        var sens = 1;
        if(num<this.nbCurrent){ sens = -1;}
        var cssDeb = { "left" : sens*this.elem.width() };
        var cssFin = { "left" : -sens*this.elem.width() };
        this.elem.find("#slide"+num).show().css(cssDeb);
        this.elem.find("#slide"+num).animate({"top":0,"left":0},500);
        this.elemCurrent.animate(cssFin,500);
     
        /*
        Animation Titre + Fadein/Out sur la div visu
        */
        this.elemCurrent.find(".visu").fadeOut();
        this.elem.find("#slide"+num).show();
        this.elem.find("#slide"+num+" .visu").hide().fadeIn();
        var titleHeight = this.elemCurrent.find(".title").height();
        this.elemCurrent.find(".title").animate({"bottom": -titleHeight},500);
        this.elem.find("#slide"+num+" .title").css("bottom",-titleHeight).animate({"bottom": 0},500);
        //*/
		
        
        
        this.elem.find(".navigation span").removeClass("active");
        this.elem.find(".navigation span:eq("+(num-1)+")").addClass("active");
        this.nbCurrent = num;
        this.elemCurrent = this.elem.find("#slide"+num);
    },
    
    next : function(){
        var num  = this.nbCurrent+1;
        if(num  >this.nbSlide){
            num  = 1;
        }
        this.gotoSlide(num);
    },
    prev : function(){
        var num  = this.nbCurrent-1;
        if(num< 1){
            num= this.nbSlide;
        }
        this.gotoSlide(num);
    },
    stop : function(){
        window.clearInterval(carrousel.timer);
    },
    play : function(){
        window.clearInterval(carrousel.timer);
        carrousel.timer = window.setInterval("carrousel.next()",4000);
    }

}

$(function(){
    carrousel.init($("#carrousel"));
});