autofokus

Autofokus, also known as autofocus, is a camera technology that automatically adjusts the lens to render a sharp image of the intended subject. The system analyzes the scene and moves the lens elements to place the subject within the correct plane of focus, reducing blur from misfocused imagery.

There are several underlying methods. Phase-detection autofocus uses a dedicated sensor or split-pixel data to estimate the needed lens position and is typically fast, especially with interchangeable lenses. Contrast-detection autofocus analyzes the image directly on the sensor, searching for the position that yields the maximum contrast and sharpness; it is highly accurate but can be slower, particularly in low light. Many modern cameras use a hybrid approach that combines both methods to improve speed and accuracy across different lighting conditions and subjects.

Autofokus operates in different modes. Single autofocus locks the focus once it has been achieved, suitable for stationary subjects. Continuous autofocus tracks moving subjects and updates focus as they move. Some systems feature subject detection, such as face or eye detection, to prioritize focusing on specific areas. Manual focus remains available as a fallback, often with aids like focus peaking to highlight sharp edges.

Implementation varies by device. Historically, autofocus relied on separate sensors and mechanical linkages, but contemporary cameras frequently implement on-sensor phase detection or rely on advanced motorized lenses. Focus performance depends on lighting, contrast, subject motion, lens quality, and the chosen focusing algorithm. Autofokus is widely used in photography and videography, including smartphones, where fast, reliable focusing enhances capture in dynamic scenes.