An autofocus mechanism that determines focus by measuring contrast in a scene. The mechanism assumes that maximum contrast means sharpest focus. So, it views the scene at different focal lengths, and measures the contrast in each. It can then narrow in on the direction of better contrast and take additional samples to refine focus. Contrast detection is a method of passive autofocus.
||You can learn more about how these systems work, and how to use them, in Chapter 7 of Complete Digital Photography, 4th edition.|