I practised and learnt about aperture control when taking photographs. I didn't manage to save or upload any images, but here is an example image of aperture control:
Aperture control is about changing the depth of field of the shot, it can be used to get effects like the ones shown in this example image.
Changing the aperture makes the background go out in and out of focus, but keeps the main image in the foreground in focus. This can be used to give an impression of distance, or to keep all attention on the model/main object being photographed.
To change the aperture and get different focus on the backgrounds, you have to change the F stops.
For a thin depth of field, you use a low F stop, for example, this image is taken with the setting F3.5
A thin depth of field is used to keep the focul range small, so the image is concentrated on the foreground object, with the background blurred.
A medium depth of field can be taken with a slightly higer setting, for example this was taken with F9.
The use of a medium depth of field gives a nice balanced shot between foreground, and background.
Aperture settings can also be altered to get a large depth of field, this image used F22.
Large depths of fields keep both the foreground and background in focus.