title: does the <picture> element in html5 make the "alt" attribute obsolete?
body: <p>Working on a portfolio for a photographer / videographer and trying to find a good balance between fast load and good image quality on mobile devices.
  So far, I'm keen to bet on the <strong>picture</strong> element to load multiple versions of the images based on device max width like so:</p>
  
  <pre><code>&lt;picture&gt;    https://stackexchange.com/users/10606791?tab=reputation
    &lt;source media="(max-width: 360px)" 
            srcset="picture_small.jpg"&gt;
  
    &lt;source media="(max-width: 640px)"
            srcset="picture_medium.jpg"&gt;
  
    &lt;source media="(max-width: 1366px)"
            srcset="picture_large.jpg"&gt;
  
    &lt;img src="picture_original.jpg" width="6000" height="4000"
            alt="Really usefull description for each image"&gt;
  &lt;/picture&gt;
  </code></pre>
  
  <p>My concern is that the "alt" attribute will be ignored all together by user agents for the first 3 versions of the picture and hope of search engines to use it is also a long shot.</p>