What is High Dynamic Range Image (HDRI)

Note how sometimes in a photo, parts are not detailed. You adjust contrast and brightness, but other parts becomes too bright or fainted out.
The solution, is to take several photos using different exposures, and then combine these photos into one. The result is is called High dynamic range image. The result is a image with high detail everywhere, which may make the image look artificial, but desirable for its detailed illustrative effect.
Example
the following are 4 images, taken with different exposure. Each one by itself is not great, but capture parts in detail.




Combined Image

Combined Image with Tone Mapping
