[Dilettante_Pro]

А без JS?

<style>
.box { position:relative;}
.cont   {
   position:relative;
   display:inline-block;
   height:100px;
   width:100px;   
}
.layer {
   position:relative;
   top:0px;
   left:0px; 
   background-color: rgba(0,0,0,0.3);
   height:100%;
   width:100%;
   z-index:2;
}
img {
   position:absolute;
   top:0px;
   left:0px;
   height:100%;
   width:100%;
   z-index:1; 
}
.layer:hover { background-color: rgba(0,0,0,0);}
</style>
<div class="box">
   <div class="cont">
      <div class="layer"></div>
      <img src="https://javascript.ru/cat/list/donkey.gif">
   </div>
   <div class="cont">
      <div class="layer"></div>
      <img src="https://javascript.ru/cat/list/donkey.gif">
   </div>
</div>