HDR is the acronym for High Dynamic Range, a post-production process (a computer thing) that is gaining popularity quickly the past few years. I’ll try to explain some of the concept following this gallery of photos. A note — some of my gallery images are single-photo renditions processed with Photoshop CS5 for a simulated HDR effect. True HDR renderings, by definition, require multiple images.
What happens is… many of the sights we observe and want to capture with the camera have both “relatively speaking” bright highlights and dark shadows. With our eyes and brain we can discern details within both those extremes (to a limit) I think somewhere in the range of 7 to 8 “spectrums” (I don’t know what that means but I think of it like “octaves” in music and the camera film or digital sensor can discern only 2 to 3 of those octaves. By using specialized software we can now blend a series of images (the very same object) that are captured with varying amounts of light (2 stops “under”, 1 stop “under”, correct to meter, 1 stop “over”, and 2 stops “over”). The software blends together these images so you have detail in both the shadows and the highlights. You’ve likely seen some of these and said “Wow!” but were not aware of how it’s done. HDR photos usually portray an extra feeling of depth and a sense of more realism. The process is not automatic — there is a certain amount of art that goes with it too.