HDR Imagery: What & How

High Dynamic Range digital photography has only been around for a couple years.  It entails shooting multiple exposures -- 1 to 3 increasingly overexposed, and 1 to 3 increasingly underexposed.  And you take a shot at regular exposure, of course.  

Photoshop merges the images in to one, with the result being great detail in the highlights (which are usually bleached and washed-out), and great detail in the shadows (which are usually just blackness).  That's why the extra shots are taken -- to capture all the details in all the areas of the frame. 

It is an awesome new technology, and as one might suspect, the output is a massive file (anywhere from 60 to 100MB).  Photoshop encodes it first, then you generally pick a high quality format with which to re-save (reformat) your creation -- usually TIFF -- in order to disseminate it.