According to Wikipedia, HDR is “high dynamic range imaging (HDRI or just HDR) is a set of techniques that allow a greater dynamic range of luminance between the lightest and darkest areas of an image than current standard digital imaging techniques or photographic methods. This wide dynamic range allows HDR images to more accurately represent the range of intensity levels found in real scenes, ranging from direct sunlight to faint starlight.”
An HDR photo is easy to spot. It has luminance in areas that a normal photo will not show. An HDR photo of a room in a sunny afternoon, for instance, will show the light coming from the sun outside and the light INSIDE the room. A normal photo of the same room will most likely show you an overexposed part for the windows or a very dark interior.
For those who are photography enthusiasts, creating HDR photos can be quite fun. This is done using both the camera and a photo editing software, such as Photoshop and Photomatix. Using both camera and computer software is basically the way to achieve HDR photography. Steps involved are taking photos of the same subject in different exposures, merging them into one HDR photo using Photoshop or Photomatix, processing the result, and then tone mapping. The procedures may sound very complicated to some people but you will be rewarded with astounding photographs. You will see from the photos below that results vary from fantastical to emotive to just pure photography magic. Give it a try!