Some examples of depth of field application;
Narrow depth of field: Shot with a Canon 20D, f2.8, 80mm, 2000th sec, 200 ISO
You can notice that shapes in the background of the image are starting to take on the shape of the lenes aperture setting. At f2.8, the aperture is basically a circle, with slightly flat edges -- and in this image we can see that the certain specs within the image are taking on the shape of the aperture setting.
Wide depth of field: Shot with a Canon 20D, f8, 100mm, 60th sec, 200 ISO
Much more of this image is in focus, as the camera has had more time to record the information throughout the entire depth of field.
