Autofocus is one of the great invisible revolutions in photography. When it works well, it disappears. A photographer raises the camera, half-presses the shutter, sees a box snap to an eye, a bird, a car, or a face, and the lens silently moves to the right position.

In the best modern systems, the camera does not simply focus; it can recognize, predict, track, and compensate. It can follow a soccer player running toward the lens, a bird crossing an uneven background, a model turning her face away and back again, or a child moving unpredictably across a room. The result feels effortless, but that ease is the product of nearly half a century of development.

Autofocus is not one technology. It is a chain of technologies working together.…