Selecting a Live View Focus Mode on a Nikon D7000
As with viewfinder photography, you can opt for autofocusing or manual focusing during Live View shooting, assuming that your lens supports both. If you use the kit lens, set the switch on the lens to the A position for autofocusing and to the M position to focus manually. (With other lenses, check the lens instruction manual for help.) Also set the Focus-mode selector on the camera to AF for autofocusing and M for manual focusing.
In Live View mode, you control autofocusing performance through these two options:
Autofocus mode: For still photography, this setting determines when autofocusing begins. For movies, it determines whether the camera locks focus or continuously adjusts focusing during the recording.
AF-area mode: With this option, you specify what part of the frame the autofocus system should consider when establishing focus.
Then you can choose from two Autofocus modes, AF-S or AF-F. The settings work as follows:
AF-S (single-servo autofocus): The camera sets and locks focus when you depress the shutter button halfway. (This autofocus setting is one of the few that works the same during Live View shooting as it does during viewfinder photography.) Generally speaking, AF-S works best for focusing on still subjects. For movie recording, you can lift your finger off the shutter button after focus is locked; the camera continues to use the established focusing distance throughout the entire recording unless you press the shutter button halfway to set and lock focus again.
AF-F (full-time servo autofocus): If you choose this setting, autofocusing begins immediately; you don't need to press the shutter button halfway. Focusing is continuously adjusted until you do press the shutter button halfway, at which point it is locked as long as you keep your finger on the button.
Unfortunately, there's a downside that makes AF-F less than ideal. If you shoot a movie with sound recording enabled, the camera's internal microphone picks up the sound of the autofocus motor as it adjusts focus. So if pristine audio is your goal, use AF-S mode and lock focus before you begin recording, or abandon autofocus altogether and focus manually. As another option, you can attach an external microphone to the camera and place it far enough away that it doesn't pick up the camera sounds.
To select the Autofocus mode setting, use either of these techniques:
AF mode button + Main command dial: Press and hold the button to highlight the Autofocus mode. (The icon appears in the same spot in the other Live View display styles.) Keep the button pressed as you rotate the Main command dial.
Live View/Movie AF menu option: You also can access the setting via this menu option, found on the Autofocus section of the Custom Setting menu.