Depth-of-Field and Focus
Technique - Technique
Dependent on the chosen aperture (f-stop), the focal length and the focus distance you have a certain depth-of-field (DOF). The DOF defines a zone around the chosen focus point where objects appear to be sharp. Beyond the (floating) border of this zone objects get blurry. Typical beginners tend to think that a good picture is a picture where everything is sharp so often small aperture values are preferred in order to maximize the depth-of-field. This assumption works fine some photographics scenes but it's certainly wrong as a general shooting philosophy.

All pictures provided by Michael Wagner.

The following picture (large aperture) isolates a small zone around the focus plane.

The next picture (same focus plane) was shot with minimal aperture to achieve max. depth-of-field.

The next shot (large aperture) isolates the foreground ...

... whereas this one prefers a different focus plane (same aperture).

As you can see we have lots of potential creativity just by selecting the aperture and focus plane.