Photo Mechanic is a RAW previewer. When you open a Contact Sheet with RAW, you will see the embedded raw preview. 

RAW rendering is handled through Adobe DNG Converter, which is a free download.

  1. Download and install DNG Converter. 
  2. Navigate to File>Preferences> Render Cache. 
  3. Specify the location of DNG Converter.
  4. Check Enable RAW Rendering.