How can I vertically center text over a responsive image?

Question

How can I get the caption text on these images to move around when then the browser window is resized? My implementation is jicky and I need a way to keep the text from sliding around when the window is resized.

Codepen

<div class="row">
  <div class="col-md-6">
    <img src="http://placekitten.com/600/375" class="img-responsive" />
    <h2 class="homeImageLink">
      <span>Caption Text</span>
    </h2>
  </div>
  <div class="col-md-6">
    <img src="http://placekitten.com/600/375" class="img-responsive" />
    <h2 class="homeImageLink">
      <span>Caption Text</span>
    </h2>
  </div>
</div>

.homeImageLink {
   position: absolute; 
   top: 110px; 
   left: 0;
   text-align: center; 
   width: 100%; 
}

.homeImageLink span { 
    color: red;
    font-weight: 300;
    font-style: italic;
    text-transform: uppercase;
    letter-spacing: 15px;
    pointer-events: none;
}

Answer 1

Just add one class to parent container, make it's position relative.

.img-container {
  position:relative;
}

And then make homeImageLink absolute and give top at around 45%..

It will make it vertically centered..

.homeImageLink {
   position: absolute; 
   top: calc(50% - 24px); //24px is font size of H1 I assume 
   left: 0;
   text-align: center; 
   width: 100%; 
}

Demo here : http://codepen.io/anon/pen/bJadE