How do I vertically center caption on img hover?

I am currently having problems centering my caption inside a div upon hover. The image inside the div is bigger than the div and I want the caption to be vertically centered inside that div?

HTML

<div class="container-fluid">

    <div id="page">

<!-- GRID ITEM -->
        <div class="item s1">
            <a href="#">
                <div class="grid-image">
                    <img         src="https://upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Pleiades_large.jpg/1024px-Pleiades_large.jpg">
                </div>
                <div class="item-caption">
                    <h5>I want this to be center</h5>
                </div>
            </a>
        </div>
<!-- /GRID ITEM -->

    </div>
</div>

CSS

#page .item {
    width: calc(16.66% - 10px);
    display: inline-block;
    height: 0;
    float: left;
    padding-bottom: 16.66%;
    overflow: hidden;
    background-color: salmon;
    margin: 5px;
    position: relative;
}

#page .item.s1 {
    width: calc(50% - 10px);
    padding-bottom: 50%;
    overflow: hidden;
    background-color: navy;
}

.item > a {
    position: relative;
    display: block;
    overflow: hidden;
    color: white;
}
.item:hover .grid-image:after {
    background: rgba(0, 0, 0, .7);
}
.item:hover .grid-image > img {
    -webkit-transform: scale(1.1);
       -moz-transform: scale(1.1);
        -ms-transform: scale(1.1);
         -o-transform: scale(1.1);
            transform: scale(1.1);

}
.item:hover .item-caption {
    opacity: 1;
    z-index: 3;
  visibility: visible;

}
.item-caption,
.grid-image > img,
.grid-image:after {
    -webkit-transition: all 0.3s ease-in-out 0s;
       -moz-transition: all 0.3s ease-in-out 0s;
        -ms-transition: all 0.3s ease-in-out 0s;
         -o-transition: all 0.3s ease-in-out 0s;
            transition: all 0.3s ease-in-out 0s;
}
.item-caption {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  background: rgba(29, 106, 154, 0.72);
  color: #fff;
  visibility: hidden;
  text-align: center;
  opacity: 0;
}



.grid-image {
    position: relative;
    overflow: hidden;
}

.grid-image img {
    display: block;
    overflow: hidden;
}

.grid-image:after {
    position: absolute;
    display: block;
    content: "";
  height: 100%;
  width: 100%;
    top: 0;
    left: 0;
}

JavaScript

var $container = $('#page');
$container.masonry({
columnWidth: '.grid-sizer',
itemSelector: '.item',
percentPosition: true,
gutter: 10
});

Here's a fiddle

Thank you!

Solution

try this: http://jsfiddle.net/2stywe2t/1/

What I did:

Add a new div to your HTML, right under .item-caption.
Gave .item-caption the display: table attribute and a few others
Gave the new div display: table-cell, and vertical-align: middle
Removed position:relative from the a ancestor

Make sense?