Autofocus in a video camera is a passive system that also uses the central portion of the image. Though very convenient for fast shooting, autofocus has some problems:
- It can be slow to respond.
- It may search back and forth, vainly seeking a subject to focus on.
- It has trouble in low light levels.
- It mis-focuses when the intended subject is not in the center of the image.
- It changes focus when something passes between the subject and the lens.
Autofocus video cameras work best in bright light. Switch to manual focus in low light.