What is HDR?
Cameras can't capture what the eye can see. Most cameras are only capable of capturing an average range of the darkest to the lightest areas in a photo. This is referred to as Low Dynamic Range or LDR. The detail in the dark shadows can't be seen nor can the detail in the bright areas. New capturing techniqes and software now show the details in the whole range of light in the photographed area. This is called High Dynamic Range imagery or HDRi.
HDR photography is labor intensive. An HDR image is created by taking multiple LDR exposures of the exact same thing that are exposed for the highlights, mid- tones and shadows seperately and then merged into a single image. This is done by manually metering for a normal exposure. Then a picture is made for the dark areas. Next an exposure is made for the bright areas. A minimum of 3 exposures is required for an HDR image. Depending on the subject up to 9 exposures may be required to properly cover the light range of some subjects. A camera capable of Automatic Exposure Bracketing is usually required for this kind of photography.
Now for the post processing. All the pictures are layered and merged together. Obviously, the pictures should be taken using a tripod, other wise funny things will happen to the merged picture. After this step, the picture is "Tone Mapped". This is where "Toning" adjustments are made to the picture. After this, the photo may require a stop in Photoshop. Below is an example of the difference between a regular picture and an HDR image of the same thing. The dynamic range of the scene was very wide, from very dark to very bright. The HDR image was the result of five different exposures. The NORMAL PICTURE was the normal base exposure that was bracketed around for the HDR image. Notice difference in the clouds etc.
People would like to see in a photo what they see with their eyes!