Face Detection
A system that identifies human faces in the frame and prioritises them for focus and often for exposure.
In depth
Face detection changed autofocus from a geometric problem into a semantic one: instead of asking which region has the most contrast, the camera asks where the person is. Early implementations needed a frontal, well-lit face; modern ones track profiles, partial occlusion and multiple faces, letting the photographer cycle between them.
Examples in practice
In a group shot, face detection places focus on the row of faces rather than the shoulders nearest the camera.