AF sensor is the component in a camera that detects focus by measuring contrast, phase difference, or other optical signals from the subject. It works in conjunction with the camera's autofocus system to determine the correct lens position, ensuring sharp and accurately focused images. AF sensors are critical in DSLR, mirrorless, and advanced compact cameras, enabling fast and precise focusing in various lighting conditions and shooting scenarios. High-quality AF sensors improve accuracy in portrait, action, wildlife, and sports photography, allowing photographers to capture crisp, professional-grade images even with moving subjects or complex compositions.