When taking a photograph a camera will attempt to expose the image as best as possible. However, regardless of how expensive the camera there will always be portions of the scene that are not visible — shadows that end up pure black, or bright spots that end up pure white. The amount of tones between the darkest black and the brightest white is known as the dynamic range.
Contrary to popular belief, a camera actually has a higher dynamic range than the human eye. At any given instant, an eye can discern a dynamic range of just over 6 stops, whereas a high end digital camera can resolve up to 11. However, as you eye moves around a scene, it quickly adjusts to the amount of light you are focussing on which effectively increases the overall dynamic range of the scene up to a max of around 20 stops.
High Dynamic Range Imaging (HDR) brings a similar effect to film, by allowing the combination of many different exposures of the same scene into one image using specialized software. The final output of the process has a unique other-worldly look to it that I find interesting.
On our last camping trip I dragged my tripod along and got a chance to try taking photographs that I could use to create such an image.
Here is one of the better results of my experiments:
Note how both the rocks and the sunset are evenly exposed.
Here is a collage of the photographs used to produce the HDR image:
To take the shots, I placed my camera on the tripod and set it to manual mode. I fixed the aperture at f/8, and began taking shots at different shutter speeds, beginning from very fast to very slow. Back home, I used Photomatix to produce the final image, but there are a number of other tools you can use such as Photoshop CS2.
You can view a great collection of HDR imagery on Flickr by browsing for the HDR tag. The Wikipidia article on HDR provides a good overview as well.
Like fisheye lenses and the “Lomo look”, HDR is a bit of a novelty technique, and too much of it can become overwhelming. That said, it’s fun to try and a good reason to dig out your tripod and figure out how those manual settings on your camera work.