High-dynamic-range imaging (HDRI or HDR) is a set of techniques used in imaging and photography to reproduce a greater dynamic range of luminosity than possible using standard digital imaging or photographic techniques.
HDR images can represent a greater range of luminance levels found in real-world scenes, from direct sunlight to faint nebula. It is often achieved by capturing and then combining different exposures of the same subject matter.
Non-HDR cameras take photographs with a limited exposure range, resulting in the loss of detail in bright or dark areas. HDR compensates for this loss of detail by capturing multiple photographs at different exposure levels and combining them to produce a photograph representative of a broader tonal range.
High-dynamic-range photographs are generally achieved by capturing multiple standard photographs, often using exposure bracketing, and then merging them into an HDR image. Digital photographs are often encoded in a camera’s raw image format, because 8 bit JPEG encoding doesn’t offer enough values to allow fine transitions (and introduces undesirable effects due to the lossy compression).
The images from any camera that allows manual exposure control can be used to create HDR images. This includes film cameras, though the images may need to be digitized so they can be processed with software HDR methods.
More information on HDR in http://en.wikipedia.org/wiki/High-dynamic-range_imaging