Focus is used to highlight objects at specific distance from the camera. We can focus using manual or automatic method. Most of the lenses will have a focus ring which can be rotated to adjust the focus manually. Manual focus is suitable for situations where object is stationary. If object is moving, you will need a camera having auto focus mechanism. AF (Auto) and MF (Manual) buttons are used to indicate focus method on most of the cameras. Here is the list of AF modes.