Sharpening the World: The Mechanism and Evolution of Autofocus | Knowledge #296

Autofocus (AF), which allows cameras to instantly and accurately capture subjects, has become a standard feature in photography. The mechanism involves the camera body determining "where to focus" and the lens adjusting the focus accordingly—a precise collaboration.

In recent years, advancements in AI recognition technology and silent motors for video have enabled a more flexible and accurate AF experience.

The "eyes" of AF determine where to focus on the subject. For still images or low-light conditions, contrast detection offers high precision. On the other hand, phase detection is essential for fast-moving subjects or continuous shooting.

In the latest mirrorless cameras, hybrid AF, which combines these methods, has become mainstream, achieving a balance of speed and precision.

The lens motor drives the focus. Starting with traditional DC motors, today’s options include ultrasonic motors (USM), stepping motors (STM), linear motors, and advanced designs like VXD and VCM, which prioritize silence and precision.

For video shooting, STM and linear motors are particularly valued for their ultra-quiet operation.

To maximize AF performance, settings and composition techniques are crucial. Use AF-C (Continuous AF) for moving subjects and AF-S (Single AF) for still objects.

Additionally, using central single-point AF or spot AF allows precise focusing on small subjects or in complex backgrounds. Incorporate focus lock and composition adjustment techniques for even better results.