index.html

<header class="hero">
  <div class="hero--backdrop backdrop"></div> <!-- This div only exists to hold background image  -->
  <div class="hero--content container">
      <h1>A Quirky new product</h1>
      <p class="tagline">Our product does something <strong>slightly different</strong> than its competitors</p>
      <button>BUY! DON'T THINK, BUY IMMEDIATELY.</button>
  </div> <!-- /.hero--content -->
</header>

<div style="text-align: center; margin-top: 50px;"> <!-- Filler content to show scroll effect -->
  <h2>more content</h2>
</div>

style.css

.hero {
  height: 100vh;
  background: #0ac; /* Adjust this to change filter color */
  color: #fff;
  overflow: hidden;
}

.hero--content {
  margin-top: 25vh;
  text-align: center;
}

.backdrop { /* backdrop general styles */
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
}

.hero--backdrop { /* specific backdrop styles */
  background-image: url(https://upload.wikimedia.org/wikipedia/commons/e/e8/Neuschwanstein_Castle_LOC_print_rotated.jpg);
  background-size: cover;
  background-attachment: fixed;
  opacity: 0.3; /* Adjust this to change filter density */
}

/* extra styles to make things pretty */

body {
  margin: 0;
  height: 180vh;
}

.hero--content h1 {
  font-weight: 900;
  font-size: 2.8em;
  text-transform: uppercase;
}

.hero--content button {
  color: #fff;
  border-color: #fff;
}

.hero--content p.tagline {
  font-size: 1.2em;
}