autofocussen

Autofocussen is the automatic adjustment of the focus of a camera or imaging system to render a subject sharply at a chosen distance. It replaces manual focusing and is standard in most consumer cameras, smartphones, video cameras, and many machine-vision systems. The goal is to position the lens so that the image on the sensor is at its highest sharpness.

Autofocus mechanisms fall mainly into three categories. Contrast-detection autofocus analyzes the image on the sensor and moves the lens to maximize local contrast, which correlates with sharpness. It is common in compact cameras and many smartphones, especially in live-view or video modes, but can be slower in low-contrast or low-light scenes. Phase-detection autofocus uses a dedicated sensor or on-sensor phase-detection pixels to compare two light rays and estimate the required lens adjustment, enabling faster focusing and better subject tracking. It is widely used in DSLRs and many mirrorless cameras. Active autofocus emits an external signal, such as a laser, infrared, or ultrasonic pulse, to estimate distance and set focus, which can help in low light or macro work. Hybrid systems combine multiple methods to improve speed and accuracy across situations.

Autofocus systems offer several operating modes. Single autofocus focuses once when the shutter or a button is pressed halfway, suitable for stationary subjects. Continuous autofocus keeps adjusting focus while the subject moves, helpful for tracking action. Manual override allows the photographer to fine-tune focus if needed. Autofocus performance can be affected by low light, low contrast, moving subjects, or calibration of the lens and sensor.