HDR Images Tame Highlights
One strength of high dynamic range photography is the ability to tame highlights, which are often blown out in traditional photos — that is, the camera ran out of room to store brightness information.
When that happens, the camera sensor throws its hands up in the air and exclaims, “¡No más!” The blown areas have very little detail and may be completely white, as in the sky of the left image in this figure.
In the left image, the street, bridge, and lamppost in the foreground are all decently exposed although not perfectly — they are, along with the trees, a bit dark. The sky is the bigger problem: It suffers from being mostly dead — that is, blown out. It’s too light to see many details, especially over the building to the right.
The camera got caught in the middle. It ended up favoring the foreground (although imperfectly) and therefore blew out the sky.
However, the same scene shot and processed as HDR is shown on the right side of the figure. It is overwhelmingly better. In particular, the sky has many more details and is no longer washed out. The brackets provide the information and the HDR application uses them to access and manipulate the data.
The clouds are dramatic, and the contrast between clouds and sky is much more interesting. This particular look — somewhat dramatic with plenty of surface details — was achieved during tone mapping. The trees are nice and bright, and the texture of the concrete bridge has been enhanced. In particular, the tree line was dodged — a process that selectively lightens an area.
This shot reveals
The high end of dynamic range: Normal photos often lose information to blown highlights. When the camera exposes the shadows brighter, highlights get blown out. It’s a no-win situation.
Rescuing details from blown highlights: HDR tames highlights and preserves important information. It allows you to emphasize details and contrast while preserving the entire scene. The entire photo looks better.