Shadow Over Image via Position Relative

gistfile1.txt

HTML:
<div class="block1">
  <img src="images/charlize_theron_1.jpg" width="480" height="300">
</div>

CSS:
.block1{
  box-shadow: inset 0 0 6px 4px rgba(0,0,0,.7);
  width: 480px;
  height: 300px;
}

.block1 img{
  position: relative;
  z-index: -2;
}