title: Make Blend Modes in SVG actually work?
body: <p>I've many times done the following:</p>
  
  <pre><code>&lt;defs&gt;
  &lt;filter id="screen"&gt;
  &lt;feBlend mode="screen"  in2="BackgroundImage"/&gt;
  &lt;/filter&gt;
  &lt;/defs&gt;
  </code></pre>
  
  <p>But when I, inside a shape, write "filter="url(#screen)", my shape disappears.
  I've tried it in every browser (Safari, Chrome, Firefox, FfxNightly). What am I doing wrong?</p>
  
  <p><strong>It would help if someone could give me an example that they know works</strong></p>
  
  <p>Thanks</p>