🔬 Diffraction Limit Calculator
Choose your sensor and resolution to find the aperture where diffraction begins to limit sharpness.
Diffraction-limited aperture
f/4.5
softening begins beyond this
Pixel pitch
6 µm
Airy disk at f/11
14.76 µm
⚠️ At f/11 the Airy disk is larger than a pixel — you're in the diffraction-softened range. For maximum per-pixel sharpness, stay near f/4.5 or wider.
Stopping down (higher f-number) increases depth of field but also grows the Airy disk — the blur circle from diffraction — as d = 2.44 · λ · N (λ ≈ 0.55 µm). When it exceeds the pixel pitch, fine detail softens. The diffraction-limited aperture is where the Airy disk first equals a pixel; it\'s a guide, not a hard cutoff, and stopping down a little past it is often worth it for the extra depth of field. 🔒 In your browser.
How the diffraction limit calculator works
Stopping the lens down (higher f-number) deepens focus but also spreads each point of light into a larger "Airy disk" through diffraction, of diameter d = 2.44 · λ · N (λ ≈ 0.55 µm green light, N the f-number). When that disk grows bigger than a sensor pixel, fine per-pixel detail starts to soften. The tool estimates your pixel pitch from the sensor size and megapixels, then reports the diffraction-limited aperture — the f-number where the Airy disk first equals a pixel — and whether your chosen aperture is already in the softened range.
This is a guide, not a hard wall: image detail degrades gradually past the limit, and the extra depth of field from stopping down is often worth a touch of diffraction softening — landscape shooters routinely use f/11–f/16 knowing this. Higher-resolution sensors have smaller pixels and so hit diffraction at wider apertures, but they still resolve at least as much detail as lower-resolution ones at the same aperture.
Frequently asked questions
What is the diffraction-limited aperture?
The f-number at which the Airy disk (the blur from diffraction) grows to the size of one sensor pixel. Beyond it, stopping down further reduces per-pixel sharpness. For a 24 MP full-frame sensor it's around f/6.7–f/8.
At what aperture does diffraction start?
It depends on pixel size: smaller pixels (higher resolution or smaller sensors) soften at wider apertures. This calculator computes it for your sensor and megapixels — commonly f/8–f/11 on full frame, wider on crop and phone sensors.
What is the Airy disk?
The smallest spot a lens can focus a point of light into, limited by diffraction. Its diameter is 2.44 · λ · N, so it grows as you stop down. When it exceeds a pixel, the sensor can no longer resolve finer detail.
Should I avoid stopping down past the diffraction limit?
Not necessarily. Detail softens gradually, and the extra depth of field is often more valuable than perfect per-pixel sharpness — f/11 to f/16 is common in landscapes. Treat the limit as the point where you weigh sharpness against depth of field.
Do high-megapixel cameras suffer more from diffraction?
They reach the diffraction limit at wider apertures because their pixels are smaller, but they never resolve less than a lower-resolution sensor at the same aperture — you just see the softening at 100% earlier. Downsized to the same output size, more megapixels still help.