Want to create images that have a wider range of brightness and contrast? Want your digital photos to pop off the page?
Then you need to learn about high dynamic range (HDR) imaging, a special type of digital photography designed to capture the largest possible range between the dark and bright areas of a photograph. HDR imaging involves taking multiple shots of a subject at different exposure levels, then merging the different shots into a single photographic image. All you need is a digital camera than allows for manual exposure and a digital image editing program with an HDR merge function — like Adobe Photoshop CS. The result is eye-popping images that look unlike anything you’ve taken before!
Understanding HDR Imaging
HDR stands for high dynamic range, and HDR imaging is just as the name implies — a way to create digital images with a high dynamic range in terms of luminance (brightness). That is, with HDR imaging, the range between the lightest and darkest areas of a photograph is greater than with traditional photography or digital imaging.
The wide dynamic range of an HDR image makes the picture almost pop from the page. At the most basic, HDR images more accurately represent the range of brightness levels found in real life; when applied properly, HDR brings a kind of hyperrealism to your photographs.
As an example, Figure 1 shows a digital photograph shot and edited using traditional methods. Figure 2 shows the same image captured with HDR imaging. As you can see, the HDR image is more vivid, almost surreal in its range between dark and bright areas. HDR affects everything about the picture, resulting in more defined details, sharper contrast, and more vivid colors.
Figure 1 A cloud shot using traditional imaging techniques.
Figure 2 The same cloud shot, processed with HDR imaging techniques – note the enhanced contrast, color, and dynamic range.
The increased dynamic range in an HDR image is a result of merging multiple photographs of the same subject, taken at different exposures. The exposure determines how much light is captured by the camera, and is measured in terms of exposure value, or EV. (One EV unit is equivalent to one f/stop on your camera.) An increase of one EV doubles the amount of light captured.
Taking a series of photos at different exposures is called exposure bracketing. A typical HDR image is composed of three or more images with exposures at least one EV away from each other. A dark exposure captures detail in bright areas of the scene; a light exposure captures detail in mid-tones and shadows. The over- and under-exposed shots are combined to create a finished image with more overall tonal detail than is possible with a single (proper) exposure.
The best HDR photos involve a scene of extreme contrast, in terms of brightness. That is, HDR is best shown off with photos that have both extremely bright and dark areas, such as the sun behind a darkened wall, or a dark room with bright light shining in from the windows.
By the way, HDR imaging isn’t a new phenomenon, although it has acquired a new life in this new age of digital imaging. The concept of merging several exposures dates back to the “combination printing” of French photographer Gustave Le Gray in the 1850s, and is closely related to the sophisticated burning and dodging techniques popularized by Ansel Adams in his high contrast nature photography. With the advent of digital photography and digital image editing, however, it is now feasible to accomplish HDR by combining multiple images shot at different exposures.