High Dynamic Range Images

The dynamic range of an image is, somewhat loosely speaking, a measure of the difference between the dark and light areas of the image. All capture devices and all output devices have limited dynamic range although some have a greater dynamic range than others.

Many photographs have areas of pure white or pure black; that is, there are areas without detail. A choice frequently faced by a photographer is “Should this image reveal detail in the highlights or in the shadows”. The choice must be made because of limited dynamic range.

By taking several exposures, the entire dynamic range of a scene can be captured. Since some cameras have automatic exposure bracketing, it is very convenient to get three exposures: one exposure is “correct”, one is underexposed by two stops (-2) and one is overexposed by two stops (+2). Somewhat better results can be obtained with more exposures. The images shown here were made with three to seven exposures.

The bracketed exposures must be combined to make a single high dynamic range (HDR) image and then converted into a conventional image file.  Processing can be done in Adobe Photoshop as well as dedicated software such as Photomatix.