Attached Link: http://www.debevec.org

Definitive information on HDRI in general is located at the link above. Dr. Paul Debevec invented this stuff. You can also download HDRShop there for free. It analyzes HDR images and generates the coordinates, color info, and intensity for a corresponding light dome. Useful if your application (i.e. Poser ) doesn't support HDRI directly. In fact, I believe this is how Shademaster created the 'RenderUpgrade' light set.