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Hyperfocal distance is a distance used in optics and particularly in photography.

There are two commonly used definitions of hyperfocal distance, leading to values that differ only slightly.

The first definition: the hyperfocal distance is the closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp; that is, the focus distance with the maximum depth of field. When the lens is focused at this distance, all objects at distances from half of the hyperfocal distance out to infinity will be acceptably sharp.

The second definition: the hyperfocal distance is the distance beyond which all objects are acceptably sharp, for a lens focused at infinity.

The distinction between the two meanings is rarely made, since they are interchangable and have almost identical values. The value computed according to the first definition exceeds that from the second by just one focal length.

Acceptable Sharpness

The hyperfocal distance is entirely dependent upon what level of sharpness is considered to be acceptable. The criterion for the desired acceptable sharpness is specified through the circle of confusion diameter limit. This criterion is the largest acceptable spot size diameter that an infinitesimal point is allowed to spread out to on the imaging medium (film, digital sensor, etc.).

Formulae

The hyperfocal distance is the square of the focal length divided by both the f-number and the circle of confusion limit chosen.

${\displaystyle H={\frac {F^{2}}{N\cdot C}}}$

where

H is hyperfocal distance

F is focal length

N is f-number (${\displaystyle F/D}$ for aperture diameter ${\displaystyle D}$)

C is the circle of confusion limit

This formula is exact for the second definition, if H is measured from a thin lens, or from the front principal plane of a complex lens; it is also exact for the second definition if H is measured from a point that is one focal length lenght in front of the front principal plane. Another commonly used formula for the first definition is

${\displaystyle H={\frac {F^{2}}{N\cdot C}}+F}$

Example

As an example, let's compute the hyperfocal distance for a 50 mm lens at ${\displaystyle F/16}$ using a circle of confusion of 0.03 mm (which is a value typically used in 35mm photography):

${\displaystyle H={\frac {(50{\mbox{ mm}})^{2}}{(16)(0.03{\mbox{ mm}})}}=5208{\mbox{ mm}}\,}$

If we focus the lens at a distance of 5.2 m, then everything from half that distance (2.6 m) to infinity will be acceptably sharp in our photograph. With the more exact formula for the first definition, the result ${\displaystyle H=5258{\mbox{ mm}}}$ is not much different.

External links

• http://www.dofmaster.com/dofjs.html to calculate hyperfocal distance and depth of field
• Understanding Hyperfocal Distance and Charts: real-world use for photographers, including its shortcomings and a hyperfocal chart calculator

• Optics
• Length
• Photographic terms