Focus Modes - Nikon D5100 Experience Manual

Nikon D5100 Experience

Focus Modes

The D5100 has three different Focus Modes to choose from, typically depending if your subject
is still or moving. It also has four different Autofocus Area Modes (see below) to specify how
many of the AF points are active and how they track a moving object. You can set these two
functions in various combinations. First the Focus Modes. Focus modes are set on the
Information Display (see Figure 16 and Figure 17 for setting Focus Mode on the Information
Display):
Single-Servo AF (AF-S)
Use this mode when your subject is stationary, or still and not going to move, or if your subject
is not going to move very much, or if the distance between you and the subject is not going to
change between the time you lock focus, recompose, and take the shot. Lock focus on the
subject and recompose if necessary. When using AF-S, you can select from two Autofocus Area
Modes, either Single-Point AF where you select the AF point, or Auto-Area AF, where the
camera selects the AF point(s) for you. I suggest you nearly always select your own desired AF
point.
Continuous-Servo AF (AF-C)
Use this mode when your subject is moving. If the subject is moving towards you or away from
you, the camera will keep evaluating the focus distance, as long as the Shutter-Release Button is
kept half-pressed. You will need to use this in conjunction with the Autofocus Area Modes to
determine if and how the camera tracks the subject spatially and laterally to the surrounding AF
points, or if it will only track the subject if it remains at the initially selected AF point. If the
subject is going to be moving across your field of view, set the AF-Area Mode to the Dynamic-
Area AF mode or to the 3D-Tracking mode, because Single-Point AF will only track the
subject's distance as it moves near or far as it remains under the selected point. It will not track
lateral movement if the subject leaves the selected AF point.
Focus on the moving subject with the selected AF point when using Dynamic Area Mode or 3D-
Tracking Mode, or let the camera select the AF point in Auto-Area AF Mode, and then as long as
the Shutter-Release Button remains half-pressed the camera will track the subject to the other
focus points if it moves to them and as it moves closer or farther in distance.
Auto-Servo AF (AF-A)
This mode is a hybrid of the two other focus modes. It starts in Single-Servo AF (AF-S) mode
then changes to Continuous-Servo AF (AF-C) mode if your subject starts moving. Why
shouldn't you use this all the time, then? Well, if you are focusing and then recomposing, as you
may often be doing, your movement of the camera may fool it into thinking that the subject is
moving and your resulting focus may not be where you want it to be, or may not be as accurate
as it might be if you are using Single-Servo AF.
Manual Focus
Sometimes you may be taking several photos of the same subject from the same distance, or for
some other reason want to keep the same focus distance and not have to keep re-focusing and re-
composing. Or you may be taking multiple photos for a panorama. In these situations, turn off
the auto-focus with the autofocus switch on the lens itself (set to M) and change your camera's
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