Focus
The state where the camera lens correctly converges light from the subject, producing a sharp and clear image.
Focus refers to the state where a camera lens converges light from the subject onto the sensor, producing a sharp image. An out-of-focus photo appears blurry with indistinct edges, commonly called a soft or unfocused image.
Modern cameras feature autofocus (AF) systems using phase detection or contrast detection methods. Smartphone cameras typically offer tap-to-focus, where touching the screen sets the focus point. For moving subjects, continuous AF (AF-C or Servo AF) tracks the subject in real time.
Correcting out-of-focus blur after capture is extremely difficult, though sharpness processing can slightly enhance edges. Intentionally defocusing the background for artistic effect is achieved through depth of field control. Note that camera shake blur and focus blur look similar but have different causes.