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Diffraction limit calculator

The aperture where diffraction starts to soften fine detail on your sensor, worked out from its size and resolution, before you stop down too far.

All tools
36 × 24 mm. Circle of confusion 28.8 µm
f/8
Airy disk at this aperture
11 µm1.8 pixels across; 0.37× the circle of confusion
Pixel pitch
6 µmSensor area ÷ pixel count, square pixels
Airy disk reaches two pixels at
f/8.9Rule of thumb for visible loss at 100%
Airy disk reaches one pixel at
f/4.5
Airy disk reaches the circle of confusion at
f/21

Spans one to two pixels: fine detail starts to lose contrast. Softening builds gradually; there is no sharp cliff.

Bar chart of Airy disk diameter from 1.9 µm at f/1.4 to 43 µm at f/32. Pixel pitch is 6 µm; the circle of confusion is 29 µm.Airy disk, µm (top 43)1.422.845.68111622321 px2 pxCoC
Airy disk diameter at whole f-stops. Lines mark one pixel, two pixels and the circle of confusion; bars past two pixels are filled darker.

How it works

The method behind the numbers.

Light passing through a small opening spreads out. A point in the scene lands on the sensor as a bright disc surrounded by faint rings, the Airy pattern, and the disc gets wider as you stop down. Once it spans more than a pixel or two it blurs fine detail whatever the lens quality.

Airy diameter = 2.44 × λ × N (λ = 0.55 µm, green light) pixel pitch = √(sensor width × height ÷ pixel count) N at k pixels = k × pitch ÷ (2.44 × λ)

The criterion used here is a rule of thumb, not a physical limit: the Airy disk reaching about two pixels across. Diffraction softening is gradual, not a cliff. Detail loses a little contrast with every stop, and whether you notice depends on print size, viewing distance and how much of the frame you inspect at 100%.

  • Pixel pitch assumes square pixels across the full sensor, so it is a close estimate. Enter the megapixel count from the camera's specifications.
  • The circle of confusion is the diagonal ÷ 1500 convention. Airy disks smaller than it do not disturb a normal-sized print.
  • The f-number that matters is the effective one. Focused close, it is larger than the marked value, so diffraction arrives sooner.
  • Stopping down also deepens depth of field. Choose the aperture the picture needs; this tool tells you what it costs in sharpness.
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