Apertia

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Depth-of-field calculator: read the near and far limits

Calculate a focus zone, understand circle-of-confusion assumptions, and compare settings without confusing focal length with its equivalent.

Depth of field is a range of acceptable sharpness around the plane you focused on. It is a useful planning model, rather than a promise that every detail inside two distances will look equally sharp.

Choose your sensor, actual lens focal length, f-number and subject distance below. Keep the viewing assumptions in mind when you compare the result with a large print or a tightly cropped image.

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Enter the lens's actual focal length

A 35 mm lens remains a 35 mm lens when it is attached to an APS-C camera. Enter 35 mm and select the sensor separately. Entering a full-frame-equivalent focal length as well as changing the sensor counts the crop twice.

Use the distance from the camera's sensor-plane mark when you can measure it. An estimate is fine for exploration, but a small distance error matters much more in a close portrait than in a distant landscape.

Read a worked portrait

For an 85 mm lens at f/1.8, a 3 m focus distance and a 0.030 mm circle of confusion, the thin-lens calculation gives a near limit around 2.94 m and a far limit around 3.07 m. That is approximately 13 cm in total, with little room for a subject leaning forward.

Stop down or increase the camera-to-subject distance to explore a wider zone. Recheck framing after moving; a different composition changes the comparison.

What the model leaves out

The result does not simulate camera shake, subject motion, autofocus errors, lens field curvature or diffraction. A smaller permitted circle of confusion tightens the displayed zone. It does not alter the lens itself.

  • Check the selected distance unit before entering a value.
  • Treat the far limit of infinity as a model boundary, not unlimited detail.
  • For macro work, use the close-up guide and the lens manufacturer's information.

Questions, answered

Does a larger f-number always make a better photograph?

It increases the geometric focus zone, but exposure, subject movement and diffraction also matter. Choose an aperture for the whole photograph.

Will my settings appear automatically in Apertia?

This page does not transfer settings into the app. Enter them on your iPhone when you want to continue offline.

Sources & method

Reviewed:

Keep going in Apertia

Depth-of-field and hyperfocal calculations with a side-view diagram · One saved camera-and-lens kit free; additional kits with Pro · Offline calculations; Pro adds bokeh preview, hyperfocal tables and A/B comparison

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Keep exploring

01 / Read the guide

Choose a focus zone for a group portrait

Plan for front and back rows, then check focus, movement and exposure instead of relying on a fixed group-portrait aperture.

Read the guide ↗02 / Read the guide

Use hyperfocal distance without sacrificing the foreground

See what hyperfocal focus means, how the near limit changes, and when a foreground subject needs a different approach.

Read the guide ↗03 / Read the guide

Plan close-up depth of field with the model's limits in view

Use small focus changes, align the subject and recognise when simple depth-of-field calculations stop describing macro work well.

Read the guide ↗

Measure focus distance from the sensor plane

Select a sensor preset, enter the actual focal length and f-number, then state the focus distance in millimetres from the sensor plane. The native thin-lens model handles its sensor-plane convention explicitly. Using a distance measured from a different reference can produce a different result, especially nearby.

The circle of confusion is an assumed acceptance threshold for this plan. The near and far distances describe that model, not a universal boundary between sharp and unsharp. Infinity is reported as an explicit state when the far limit is unbounded.

Check real lens behaviour

Lens design, focus breathing, aberrations, diffraction, motion, output size and computational photography can all affect a real image. Use the result to plan and compare settings, then check the photograph.

Method and reference context

A thin-lens plan using distances from the sensor plane. Real lens behaviour, focus breathing and computational photography are outside this model.

Inputs

mm
f-number
mm

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