title: Matlab imnoise Poisson doing nothing?
body: <p>Basically I have:</p>
  
  <pre><code>sourceImage = im2double(imread(srcPath));
  
  noiseImage = imnoise(sourceImage,'poisson');
  </code></pre>
  
  <p>The problem is that both sourceImage and noiseImage look pretty the same.</p>
  
  <p>Indeed if I do </p>
  
  <pre><code>norm(sourceImage - noiseImage)
  </code></pre>
  
  <p>I get <code>1.4810e-05</code> (this seems a too low difference)</p>
  
  <p>Am I doing it wrong?</p>