Q:

div background ease with transparent overlay on hover

I have created a div that has a transparent overlay when user hovers on it. How is it possible to make the background image ease slightly to create a nice effect when the overlay happens. An example would be something similar to what is happening on the work section of this website. 
HTML
<ul class="portfolio-project-image">
<li><a href="images/flyer_mock_up.jpg">
    <span>
    Marks &amp; Spencer 
    <span>Summer Fete A5 Flyers</span>
     </span>
    </a>
</li>

CSS
body{
    font: 200 14px/1.3 'Roboto', 'Helvetica Neue', 'Segoe UI Light', sans-serif;
}

ul.portfolio-project-image{
    margin:10px;
    padding:0;
    text-decoration:none;
    list-style-type:none;

}

ul.portfolio-project-image li a,
ul.portfolio-project-image li a>span{
    display:block;
    width:200px;
    height:300px;
    text-align:center;
    background:#fabada;
    position:relative;
    box-sizing:border-box;
    overflow:hidden;

}

ul.portfolio-project-image li span{
    display:block;
}

ul.portfolio-project-image li a>span{
    padding-top:80px;
    background:#fe0;
    position:absolute;
    top:-100%;
    -webkit-transition: top 0.3s ease-in-out;
            transition: top 0.3s ease-in-out;
}

ul.portfolio-project-image li a:hover>span{
    top:0%;
}

See the demo in my JFIDDLE 

A:

i think this person may have what you are looking for
https://jsfiddle.net/NewsletterPolls/yy4q7jqg/ 

body{
    font: 200 14px/1.3 'Roboto', 'Helvetica Neue', 'Segoe UI Light', sans-serif;
}

ul.portfolio-project-image{
    margin:10px;
    padding:0;
    text-decoration:none;
    list-style-type:none;
    
}

ul.portfolio-project-image li a,
ul.portfolio-project-image li a>span{
    display:block;
    width:200px;
    height:300px;
    text-align:center;
    background:#fabada;
    position:relative;
    box-sizing:border-box;
    overflow:hidden;
    
}
ul.portfolio-project-image li a {
background-image: url(http://placekitten.com/g/200/300);
 background-size: 200px 100%;
 background-position: center;
    background-repeat: no-repeat;
   -webkit-transition: .5s;
   transition: .5s;
}
ul.portfolio-project-image li a:hover {
  background-size: 300px 150%;
}

ul.portfolio-project-image li span{
    display:block;
}

ul.portfolio-project-image li a>span{
    padding-top:80px;
    background:#fe0;
 opacity: .8;
    position:absolute;
    top:0%;
    -webkit-transition: top 0.3s ease-in-out;
            transition: top 0.3s ease-in-out;
}

ul.portfolio-project-image li a:hover>span{
    top:-100%;
}
<ul class="portfolio-project-image">
    <li><a href="images/flyer_mock_up.jpg">
        <span>
        Marks &amp; Spencer 
        <span>Summer Fete A5 Flyers</span>
         </span>
        </a>
    </li>
</ul>

added opacity to make this example more like the link you provided

