How HDR Keeps a Bright Sky and a Shadowed Street
A camera sensor can record only a limited range of brightness in one exposure. If it is set to preserve detail in a bright sky, a shaded building may turn nearly black; if it is set for the building, the sky may lose its cloud detail and become a blank white patch. High dynamic range (HDR) photography is designed to bridge that gap.
How the Exposures Become One Image
The camera captures versions of the scene with different exposure settings. A shorter exposure preserves detail in bright areas, while a longer one records more information in dim areas. Software aligns the frames, compares their brightness, and draws on the useful parts of each to produce a single image.
That alignment matters: if a person or car moves between shots, the versions may not line up cleanly. The result can be a faint double edge or a patch that looks strangely smeared. Cameras reduce this problem with fast capture and processing, but scenes with motion can still challenge HDR.
Why the Result Can Look Unnatural
Combining exposures does not simply make every part of a picture equally bright. The camera must map a wide range of recorded light onto a screen or print, which cannot show all of it at once. This process, called tone mapping, determines how the final contrast and colors appear. Applied gently, it can preserve a believable balance; pushed too far, it can flatten contrast and make edges or colors look exaggerated.
The practical benefit is detail in both ends of a difficult scene—such as clouds above a dark doorway—without forcing the photographer to choose which one disappears.
