AF Area Selection Modes
Single-point Spot AF (Manual selection)
Although this is the same as Single-point AF, the selected AF point <O> covers a smaller area to focus. Effective for pinpoint focusing of overlapping subjects such as an animal in a cage. Since Spot AF covers a very small area, focusing may be difficult during hand-held shooting or for a moving subject.
Single-point AF (Manual selection)
Select one AF point <S> to be used for focusing.
AF point expansion (Manual selection 
)
The manually-selected AF point <S> and adjacent AF points <w> (above, below, on the left and on the right) are used to focus. Effective when it is difficult to track a moving subject with just one AF point. With AI Servo AF, the manually-selected AF point <S> must focus- track the subject first. However, it is easier to focus the target subject than with Zone AF.
With One-Shot AF, when focus is achieved with an expanded AF point, the expanded AF point <S> will also be displayed along with the manually-selected AF point <S>.