With HDR, the photographer makes a series of widely-bracketed exposures of a specific scene, so that even with extremely contrasty subjects one shot or another will record detail in the brightest highlights and deepest shadows. (For proper registration, this is best done with the camera on a tripod.) These exposures are then "merged" by the software to produce a single 32-bit image, which is crunched back into a smaller bit space but which still contains a wider range of tones (within the limits of monitors and printers) than a single exposure would have produced. This means you can hold good detail, for example, in both a dark interior and the brilliant, sunlit scene visible through its windows. All it takes is a few brackets and some mouse clicks -- no carefully-balanced, supplemental inside light required.