(This diagram shows an image ... Bailey demonstrates how to use space, zoom and aperture (or iris) to create a shallow, or narrow, depth of field.

The basic concept behind the extended depth of field is that a specially designed phase plate is inserted at the back aperture of the microscope objecive. The phase plate creates a uniquely shaped PSF ...

The wider the aperture (the smaller the f-stop number), elements in front of and behind the object in focus appear soft or blurry. In both moving and still pictures, depth of field (DOF ...

where everything is in focus Depth of field is controlled by the aperture. A larger aperture means a narrower depth of field.