Explanation: Pressing the round button allows you to change autofocus settings with the command dials. The following applies to „normal“ photography using the viewfinder, not to the live miew mode that is described separately. You can change:
1. The method of focus tracking with the main command dial on the back:
AF-A: The D7000 tries to recognize moving subjects and decides automatically if the focus „locks“ once it could focus successfully or if it is continuously adjusted.
AF-S („single auto focus“): The D7000 focuses only once when you press the shutter release button halfway and will then keep the focus until you release the button and press it again halfway.
AF-C („continuous auto focus“): The D7000 focuses continuously to track moving subjects as long as you keep the shutter release button pressed halfway.
2. The focus point selection together with the sub command dial at the front:
AUTO: Automatic selection, i.e. one or several focus points will be selected by the camera electronics and highlighted in the viewfinder.
3D: The D7000 focuses initially with a single focus point that you can choose and when tracking a moving subject it will use all 39 focus points when your subject moves in the viewfinder.
This method of focus tracking uses color contrasts around the initially selected focus point.
„Dynamic area focus tracking“ : The D7000 uses initially a single focus point that you can choose and when tracking a moving subject it will also use the surrounding 9, 21 or 39 focus points when your subject gets away from the initial focus points.
These variants are for subjects that move predictably in different areas of the viewfinder.
Single focus point : The D7000 uses only the single focus point that you can select.
In all modes except AUTO the initially select focus point is highlighted in the viewfinder and can be moved with the multi selector.
In the custom setting menu a6 Number of focus points you can reduce the number of points for your manual selection from 39 down to 11.
Pressing the OK button resets the focus point selection back to the center one – unless you have changed the configuration of this button in the custom setting menu f2 OK button (shooting mode).
While the autofocus button is pressed the currently chosen settings are displayed in the viewfinder – you can change them without moving the camera away from your eye.
1. About focus tracking:
AF-A is a clever automatic and good standard setting. But I would change to AF-C if you want to be sure that the focus will track a subject. If your subjects moves irregularly a short stop at the moment you press the shutter release button can be enough for the autofocus to „lock“.
2. About focus point selection:
For not moving subjects AUTO is a good standard setting and most convenient but watch which focus points are used! The automatic can choose background or foreground depending on the subject and it cannot read your mind and guess always correctly which part you want to have in best focus.
If you want to have best focus somewhere else you need to intervene and either select manually or move the viewfinder a bit, focus, then restore your initial picture frame and take the picture.
And note: The exposure metering can give more weight to the area where the camera has focused. In other words: If the autofocus chooses the right distance but uses a part of the picture that is darker or brighter than your main subject you may not get the best exposure. This can be another reason to change to manual focus selection.
For moving subjects 3D is the best method to track focus.