High Dynamic Range photography allows us to depict the scene more accurately and with wider range of luminance. In simple words HDR image contains much more light intensity levels between the lightest and darkest areas of an image than any other standard digital imaging techniques or photographic methods. To produce an HDR image we need to take at least two or three pictures of the same scene with different exposures and then merge them into one image. To get better results we can use even over a dozen images with different exposures ranging from the brightest to the darkest spot of a scene. The camera needs to be set up on a tripod as it cannot be moved a for the best clarity of the merged image.
After merging pictures into one image another operation has to be applied, which is Tone Mapping. This technique reduces overall contrast to facilitate display of HDR images on devices with lower dynamic range.
Information stored in high dynamic range images represent physical values of luminance or radiance. Therefore they reflect better what can be observed in the real world. Unlike traditional digital images, which represent colors that should appear on a monitor or a paper print. HDR image formats are often called “scene-referred”, in contrast to traditional digital images, which are “device-referred”.
Bibliography:
Cohen, Jonathan and Tchou, Chris and Hawkins, Tim and Debevec, Paul E. (2001). Steven Jacob Gortler and Karol Myszkowski. ed. “Real-Time High Dynammic Range Texture Mapping”.
Greg Ward, Anyhere Software. “High Dynamic Range Image Encodings”. http://www.anyhere.com/gward/hdrenc/hdr_encodings.html.
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