HTML Rendered:
<p>Image added via "Insert > Image" menu, Alt text comes from this dialog.</p>
<p>
<img src="/globalassets/logotype.png" border="0" alt="Alt Text from insert dialogue" />
</p>
<hr />
<p>Image added by dragging from media tab. Alt text is auto populated from the name property.</p>
<p>
<img src="/globalassets/logotype.png" border="0" alt="logotype.png" />
</p>