Hyperfocal distance

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Hyperfocal distance explained

What it is
- The hyperfocal distance is the closest distance at which everything from half that distance to infinity can be kept acceptably sharp when you focus the lens at that distance. It helps you maximize depth of field on fixed-focus cameras.

What it depends on
- It depends on the lens focal length (f), the aperture (f-number N), and how sharp you want things to appear (the circle of confusion, c). The CoC encodes what level of blur is acceptable for your sensor size and print size.

Two common definitions
- There are two closely related formulas. In simple terms, the practical one you’ll see is H ≈ f^2 / (N c). A more exact form adds a small f term (H ≈ f^2/(N c) + f), but the difference is tiny for most situations.

Consecutive depths of field
- A neat property: if you focus at H, the depth of field extends from H/2 to infinity. If you focus at H/2, it extends from H/3 to H, then at H/3 it’s from H/4 to H/2, and so on. This is called consecutive depths of field.

A quick example
- Suppose you have a 50 mm lens at f/8 and you use a circle of confusion of 0.03 mm. Then H ≈ 50^2 / (8 × 0.03) ≈ 10,417 mm ≈ 10.4 m.
- If you focus at about 10.4 m, everything from roughly 5.2 m to infinity will look acceptably sharp.

Practical notes
- Many lenses have DOF scales or focus marks for hyperfocal distances at common f-stops.
- The two most common definitions give almost the same number in practice; the exact value changes by about one focal length, which isn’t important in everyday shooting.

History (very short)
- The idea goes back to 19th and early 20th-century work by photographers and optical researchers. Over time, the term hyperfocal distance and its formulas were clarified and named, with different but very close ways to calculate it.

How to use it
- Choose your format’s CoC (depends on sensor/print size).
- Pick your focal length and aperture.
- Compute H ≈ f^2 / (N c). Focus at H to maximize depth of field.
- If you don’t have a calculator, many lenses’ DOF scales or cameras can help you estimate quickly.