The Hyperfocal Distance or Depth of Field

This is the distance approach achieved greater depth of field, extending it from half the distance to infinity.

Imagine the following experiment: in a landscape we will set the focus to approach to infinity; then we try to find the closest object to us which is still the most acceptable focused object, this is the nearest limit of the current field depth.

 

 

If we fix this and now we focus to that point  we will achieve keep sharp plain infinity and we will have obtained an extra depth of field in front of the focused point, about half of the distance from the object to us. The found point is located at the hyperfocal distance.

 

In formulas:

Hyperfocal distance: H = (L2 / (f d)) + L

Where:

H = hyperfocal distance (in millimeters) L = focal length of the objective, the real, not the equivalent according to factor clipping (in millimeters)
f = diaphragm opening
d = diameter of the circle of confusion - see definition below-(in millimeters)

Some 'd' values

-In film: for 35 mm d = 0.03
-In digital: for FF d = 0.03; for 1.6 factor d = 0,019; to factor 1.5 d = 0.022.

They are general values that vary depending on the size of the photo sensors and its density.