Diffraction Limit Calculator
Airy disk diameter, the f-number where diffraction reaches the pixel pitch, and whether it is visible yet.
Results
Airy disk diameter
14.7580
µm
Pixel pitch
6.000
µm
f-number where the disk equals one pixel
4.47
f-number where it equals two pixels
8.94
f-number where it equals the circle of confusion
21.62
Airy disk in pixels
2.460
Is diffraction showing?
Clearly — the disk spans more than two pixels
Line pairs it resolves
165.3
lp/mm
Megapixels the optics can feed
3.97
MP
What this tool does
Stopping down deepens the depth of field and, past a point, softens everything in it. The point is where the Airy disk — the smallest spot a perfect lens can make — grows past what the sensor can resolve. That has nothing to do with lens quality: it is the wavelength of light and the f-number, and no lens can beat it. The page says where your sensor crosses that line. The constant 2.43934 is twice the position of the first dark ring; 2.44 is the rounding you will see quoted, and it differs by three parts in ten thousand.
Formula
Airy disk = 2.43934 λ N · N where the disk matches the pixel: N = p ÷ (2.43934 λ)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
ap | f-number | — |
lam | Wavelength of light | nm |
sw | Sensor width | mm |
px | Pixels across the sensor | — |
cc | Circle of confusion | mm |
AD | Airy disk diameter | µm |
PP | Pixel pitch | µm |
NP | f-number where the disk equals one pixel | — |
NN | f-number where it equals two pixels | — |
NC | f-number where it equals the circle of confusion | — |
RA | Airy disk in pixels | — |
VB | Is diffraction showing? | — |
LP | Line pairs it resolves | lp/mm |
MP | Megapixels the optics can feed | MP |
Worked example
- f-number11
- Wavelength of light550 nm
- Sensor width36 mm
- Pixels across the sensor6000
- Circle of confusion0.029 mm
- Airy disk diameter14.7580 µm
- Pixel pitch6.000 µm
- f-number where the disk equals one pixel4.47
- f-number where it equals two pixels8.94
- f-number where it equals the circle of confusion21.62
- Airy disk in pixels2.460
- Is diffraction showing?Clearly — the disk spans more than two pixels
- Line pairs it resolves165.3 lp/mm
- Megapixels the optics can feed3.97 MP
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.