The Depth of Field tab lets you calculate the depth of the field of acceptable sharpness in a print. This depends primarily on the subject distance, focal length, aperture, and the circle of confusion. The program calculates the CoC value based on the film size, but you can put your own value in, if you like.
When you focus your camera's lens at a certain subject distance, objects at exactly that distance from the camera are exactly in focus. Technically, everything else is out of focus. In practice, however, there is a "zone of acceptable focus" surrounding the focus plane, so that objects within that zone are considered "in focus" and those outside that zone are "out of focus". The size of this zone is called the "depth of field."
General Rules About Depth of Field:
First, we must find the hyperfocal distance:
where f is the focal length of the lens, A is the aperture value and c is the circle of confusion value.
The near edge of the zone of acceptable focus is found with:
and the far edge is found with:
where h is the hyperfocal distance calculated above, and s is the subject distance.
All lengths f, c and s must be in the same unit, such as millimeters.