This info is written to the header of the file and only for auto saved renders. For info on how to read the headers see the documentation for the relevant format. I don't believe GIMP has a way to view this data. As [ideasman42 said][1], for EXR files you can use `exrheader` which is included in the [OpenEXR] package.

  [1]: http://blender.stackexchange.com/questions/463/logging-renders/464#comment-594
  [OpenEXR]: http://www.openexr.com/