Diffraction limit: what aperture detail starts dropping at
Closing the aperture suppresses aberrations, but past a point diffraction takes over: light bends around the aperture's edge, and a point renders as a spot. The calculator shows where that line sits for your sensor.
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This is the diffraction limit, not the optimal aperture: below it, quality is limited by lens aberrations, which fall as you close down instead. Find your own sweet spot by testing.
How it's calculated
- Pixel pitch comes from sensor size and megapixel count: more pixels on the same area means each one is smaller.
- A closed aperture turns a point into an Airy disk, and its diameter grows directly with the f-number.
- Detail starts dropping once the disk covers about two pixels — that's where the limiting aperture comes from.
Example: A 24 MP full-frame sensor → a 6 μm pixel pitch. At f/8 the Airy disk is 10.74 μm, or 1.8 pixels — still within limits. Diffraction starts limiting from about f/8.9.
Airy disk diameter d ≈ 2.44·λ·N at λ = 0.55 μm (green light). Pixel pitch = sensor width ÷ horizontal resolution. Diffraction starts limiting once the disk covers about two pixels.
This is an estimate
Verify final values against current standards, the project design, and equipment nameplates.