About the Diffraction Limit Calculator
This diffraction limit calculator finds the aperture at which diffraction starts to limit the sharpness your sensor can record. Choose your sensor size and enter its megapixel count, and the calculator works out the pixel pitch, the diameter of the Airy disk at any f-stop, and the f-number where that blur spot grows larger than about two pixels — the point at which stopping down further trades fine detail for depth of field.
Landscape, architecture, product and macro photographers use it to choose the sharpest aperture for a camera, and to understand why a 45 MP body shows softening sooner than a 24 MP body when viewed at 100%. It is also a quick way to compare how sensor size and resolution interact: smaller pixels reach the diffraction limit at wider apertures.
The diffraction-limited aperture is a gradual threshold, not a cliff. Images shot one or two stops beyond it are still sharp at normal viewing sizes, and often worth it for extra depth of field. The calculation assumes green light (550 nm) by default and a perfect lens, and ignores the sensor’s anti-aliasing filter and Bayer demosaicing.
How to use the diffraction limit calculator
- 1Choose your sensor format, or enter a custom width and height.
- 2Enter the camera’s resolution in megapixels.
- 3Leave the wavelength at 550 nm and the allowance at 2 px unless you want a stricter test.
- 4Read the diffraction-limited aperture and the nearest marked f-stop.
- 5Enter the aperture you plan to use to see how large its Airy disk is in pixels.
Formula and method
Light passing through a circular aperture spreads into an Airy pattern; the diameter of its central disk, measured to the first dark ring, is 2.44 × wavelength × f-number. Pixel pitch is the sensor width divided by the number of pixels across it, which follows from the megapixel count and the sensor’s aspect ratio.
The diffraction-limited aperture is the f-number at which the Airy disk diameter equals k pixels. With the common allowance of about two pixels, detail finer than the disk cannot be resolved beyond this point, so stopping down further gives more depth of field but slightly less per-pixel sharpness. Real Bayer sensors and anti-aliasing filters blur fine detail a little anyway, which is why softening is gradual.
- p
- Pixel pitch (µm)
- W, H
- Sensor width and height (mm)
- MP
- Resolution in megapixels
- λ
- Wavelength of light (µm; 550 nm = 0.55 µm)
- N
- f-number
- k
- Airy disk allowance in pixels (default 2)
Worked examples
24 MP full-frame camera
A 24 MP 3:2 sensor is 6,000 pixels wide, so on a 36 mm sensor each pixel is 6.0 µm. Two pixels is 12 µm, and the Airy disk reaches that at 12 ÷ (2.44 × 0.55) ≈ f/8.9. At f/11 the disk is 14.76 µm, about 2.46 pixels — slightly past the limit.
45 MP full-frame camera
45 MP on a 36 × 24 mm sensor gives about 8,216 pixels across and a 4.38 µm pitch. The diffraction limit drops to about f/6.5, so at f/11 the Airy disk covers 3.37 pixels and per-pixel softening is visible at 100% view.
20 MP Micro Four Thirds at f/8
A 17.3 × 13 mm sensor with 20 MP is about 5,159 pixels wide, a 3.35 µm pitch. The limit is about f/5, which is why Micro Four Thirds shooters rarely stop down past f/8: there, the 10.74 µm Airy disk already spans 3.2 pixels.
Frequently asked questions
What is the diffraction limit in photography?+
It is the aperture at which the blur caused by light spreading through the lens opening (the Airy disk) becomes larger than the sensor can resolve — roughly two pixels wide. Beyond it, stopping down adds depth of field but reduces the finest detail your camera can capture.
Should I never shoot past the diffraction-limited aperture?+
No. Softening is gradual, and at normal print or screen sizes images one or two stops past the limit still look sharp. If you need more depth of field for a landscape or macro shot, the trade-off is usually worth it, and sharpening can recover some micro-contrast.
Do higher megapixel cameras suffer more from diffraction?+
At 100% view, yes: smaller pixels reach the limit at wider apertures. But when the whole image is viewed at the same output size, a high-resolution camera at f/11 still records at least as much detail as a lower-resolution one at f/11 — it just does not gain its full advantage.
What is pixel pitch?+
Pixel pitch is the centre-to-centre distance between neighbouring photosites on the sensor, usually given in micrometres (µm). It equals sensor width divided by image width in pixels; a 24 MP full-frame sensor has about 6 µm pitch, while phone sensors are often under 1 µm.
Does sensor size affect diffraction?+
Diffraction blur depends only on f-number and wavelength, but smaller sensors have smaller pixels for the same megapixels and must be enlarged more for viewing, so they show diffraction softening at wider apertures. This is why compact and phone cameras rarely offer apertures beyond f/8.