High Dynamic Range Images (HDRI or HDR) reproduce more closely that which the human eye sees. People have the ability to discern a much greater range of light than a camera; so HDR images are created by taking multiple images of a scene at several exposures and combining the usable portions into a wider range composite.
Usually, a computer is necessary to create these composite images, although some digital cameras are including this feature.
The HDR image is the source for derivative images and panoramas via a process called tone-mapping.
Under-exposed Image
Normal Exposure
Over-exposed Image
Composite Image