HDR -

Three exposures Fuji 4000a ( Bracket 3 -1 0 +1 ev) combined in Picturenaut . In image processing, computer graphics, and photography, high dynamic range imaging (HDRI or just HDR) is a set of techniques that allows a greater dynamic range 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 represent more accurately the range of intensity levels found in real scenes, ranging from direct sunlight to faint starlight, and is often captured by way of a plurality of differently exposed pictures of the same subject matter.[1][2][3]

In simpler terms, HDR is a range of techniques geared toward representing more contrast in pictures. Non-HDR cameras take pictures at a single exposure level with a limited contrast range. This results in the loss of detail in bright or dark areas of a picture, depending on whether the camera had a low or high exposure setting. HDR compensates for this loss of detail by taking multiple pictures at different exposure levels and intelligently stitching them together so that we eventually arrive at a picture that is representative in both dark and bright areas.

The two main sources of HDR imagery are computer renderings and merging of multiple low-dynamic-range (LDR) [4] or standard-dynamic-range (SDR)[5] 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.