What is hyperfocal distance?

It is the closest focus distance at which objects all the way to infinity stay acceptably sharp. When you focus exactly at the hyperfocal distance, the depth of field extends from half that distance out to infinity, giving the most front-to-back sharpness possible at a given focal length and aperture.

Why does it matter for astrophotography?

Milky Way shots usually pair a foreground subject with stars at infinity. Focusing at the hyperfocal distance keeps both the foreground and the stars acceptably sharp in a single exposure, avoiding the need to focus-stack or sacrifice one for the other.

What is circle of confusion?

It is the largest blur spot that still looks like a sharp point at normal viewing size. It scales with sensor size — about 0.029 mm on full frame, 0.019 mm on APS-C, 0.015 mm on Micro Four Thirds — and smaller sensors demand sharper focus, pushing the hyperfocal distance further out.

How are the near and far limits calculated?

From the hyperfocal distance H and the focus distance s, the near limit is s(H−f)/(H+s−2f) and the far limit is s(H−f)/(H−s). When the focus distance reaches or passes the hyperfocal distance, the far limit becomes infinity.

Should I focus exactly at the hyperfocal distance?

It is a great starting point, but acceptably sharp is a print standard, not pixel-level critical sharpness. For large prints or demanding work, focus slightly beyond the hyperfocal distance or stop down one more stop to give yourself a safety margin at infinity.

Astrophoto Depth of Field & Hyperfocal Distance

For wide landscape and Milky Way photography, the trick is getting both a near foreground and the stars at infinity acceptably sharp in one frame. The hyperfocal distance is the focus point that does exactly that. This calculator finds it for your lens and sensor, and shows the near and far limits at any focus distance.

How it works

The hyperfocal distance depends on focal length, aperture and how forgiving your sensor is about blur (the circle of confusion):

H = f² ÷ (N × c) + f

where f is focal length in mm, N is the f-number, and c is the circle of confusion for your format. Focus at H and everything from H/2 to infinity is acceptably sharp.

For a subject focused at distance s, the sharp zone runs between:

near = s(H − f) ÷ (H + s − 2f) far = s(H − f) ÷ (H − s)

When s reaches H, the far limit goes to infinity — that is the hyperfocal condition.

Example

A 24 mm lens at f/8 on full frame (c = 0.029 mm) gives a hyperfocal distance of about 24² / (8 × 0.029) + 24 ≈ 2.5 m. Focus there and everything from roughly 1.25 m to infinity — foreground rocks and the Milky Way — falls inside the sharp zone.

Notes

“Acceptably sharp” is judged at normal print-viewing size, so for big enlargements or critical pixel-level sharpness, focus a little past the hyperfocal distance or stop down one more stop. Smaller sensors have a smaller circle of confusion, which pushes the hyperfocal distance further away. All calculations run locally in your browser.