Code Playground

@import url(https://fonts.googleapis.com/css?family=Lato);
html, body {
  padding: 0;
  margin: 0;
  height: 100%;
}

html {
  font: 1em/1.5 "Lato", sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizelegibility;
}

body {
  font-size: 1.3em;
}

header {
  height: 100%;
  position: relative;
  overflow: hidden;
  background: url(https://unsplash.imgix.net/45/ZLSw0SXxThSrkXRIiCdT_DSC_0345.jpg?q=75&w=1080&h=1080&fit=max&fm=jpg&auto=format&s=857f07b76abac23a7fb7161cc7b12a46) center no-repeat;
  /* Image Credit: Unsplash.me */
  background-size: cover;
}
header .content {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 1;
}
header h1, header h2 {
  margin: 0;
}
header h2 {
  text-transform: uppercase;
  margin-top: -.5em;
}
header hgroup {
  -webkit-transform: translate(-50%, -50%);
  -moz-transform: translate(-50%, -50%);
  -ms-transform: translate(-50%, -50%);
  -o-transform: translate(-50%, -50%);
  transform: translate(-50%, -50%);
  display: inline-block;
  text-align: center;
  position: absolute;
  top: 50%;
  left: 50%;
  color: #fff;
  border: 5px solid #fff;
  padding: .5em 3em;
  background-color: rgba(0, 0, 0, 0.2);
  z-index: 2;
}
header .overlay {
  position: absolute;
  top: 0;
  right: 0;
  left: 0;
  bottom: 0;
  background:#333 center no-repeat;
  background-size: cover;
  z-index: 0;
  opacity: 0;  -webkit-filter: blur(4px);
}

.site {
  padding: 20em 0;
  text-align: center;
  background-color: #efefef;
  font-size: .8em;
  color: #444;
  position:relative
}
.site a {
  color: #666;
  text-decoration: none;
}
.site a:hover {
  color: #222;
}

.site nav{
  position:absolute;
  top:0;
  left:0;
  background:#222;
  width:100%
}
.site nav a{
  padding:10px 30px;
  font-size:1.3em;
  display:inline-block
}
.site nav a:hover{
  background:#333;
  color:#fff
}

//Based on the Scroller function from @sallar
var $content = $('header .content')
  , $blur    = $('header .overlay')
  , wHeight  = $(window).height();

$(window).on('resize', function(){
  wHeight = $(window).height();
});

window.requestAnimFrame = (function()
{
  return  window.requestAnimationFrame       ||
          window.webkitRequestAnimationFrame ||
          window.mozRequestAnimationFrame    ||
          function( callback ){
            window.setTimeout(callback, 1000 / 60);
          };
})();

function Scroller()
{
  this.latestKnownScrollY = 0;
  this.ticking            = false;
}

Scroller.prototype = {
 
  init: function() {
    window.addEventListener('scroll', this.onScroll.bind(this), false);
    $blur.css('background-image',$('header:first-of-type').css('background-image'));
  },

onScroll: function() {
    this.latestKnownScrollY = window.scrollY;
    this.requestTick();
  },

requestTick: function() {
    if( !this.ticking ) {
      window.requestAnimFrame(this.update.bind(this));
    }
    this.ticking = true;
  },

update: function() {
    var currentScrollY = this.latestKnownScrollY;
    this.ticking       = false;
    
    
    var slowScroll = currentScrollY / 2
      , blurScroll = currentScrollY * 2
      , opaScroll = 1.4 - currentScrollY / 400;
   if(currentScrollY > wHeight)
     $('nav').css('position','fixed');
   else
     $('nav').css('position','absolute');
    
    $content.css({
      'transform'         : 'translateY(' + slowScroll + 'px)',
      '-moz-transform'    : 'translateY(' + slowScroll + 'px)',
      '-webkit-transform' : 'translateY(' + slowScroll + 'px)',
      'opacity' : opaScroll
    });
    
    $blur.css({
      'opacity' : blurScroll / wHeight
    });
  }
};

var scroller = new Scroller();  
scroller.init();

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