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.
The main sources of HDR imagery are merging of multiple photographs which in turn are individually referred to as low-dynamic-range LDR or standard-dynamic-range SDR photographs. Tone-mapping techniques, which reduce overall contrast to facilitate display of HDR images on devices with lower dynamic range, can be applied to produce images with preserved or exaggerated local contrast for artistic effect. (Wikipedia)
"This technique is used to capture and represent the full (as possible) Dynamic Range found in a scene with high perceptual accuracy and precision. Many imaging experts regard HDR photography as the future of digital photography.
Haunting, surreal, and possibly the first major way in which digital photography does something which film photography can’t emulate – or even come near. High Dynamic Range photography is nothing new, but as new tools and techniques make the art form more available, HDR photography is taking off in a big way". (Haje Jan Kamps)