f/20
Aperture
8.6
Stops less light than f/1
0.25%
Light vs f/1
8.52 m
DoF: 50 mm at 3 m (FF)
26.8 µm
Airy disk diameter
Depth of field at f/20 (full frame)#
| Focal | at 1 m | at 2 m | at 5 m | at 10 m | Hyperfocal |
|---|---|---|---|---|---|
| 16 mm | ∞ | ∞ | ∞ | ∞ | 44.3 cm |
| 24 mm | ∞ | ∞ | ∞ | ∞ | 98.4 cm |
| 35 mm | 1.22 m | 52.2 m | ∞ | ∞ | 2.08 m |
| 50 mm | 48.1 cm | 2.40 m | ∞ | ∞ | 4.22 m |
| 85 mm | 15.3 cm | 65.3 cm | 4.90 m | 51.1 m | 12.1 m |
| 135 mm | 5.7 cm | 24.7 cm | 1.64 m | 7.26 m | 30.5 m |
| 200 mm | 2.4 cm | 10.8 cm | 72.4 cm | 3.00 m | 66.9 m |
Diffraction at f/20#
Diffraction softening becomes visible at 100% once the Airy disk spans more than about two pixels. It is a gradual effect, not a cliff.
| Sensor | Pixel pitch | Airy disk / pixel | Pixel-level sharpness |
|---|---|---|---|
| Full frame 24 MP | 6.00 µm | 4.5× | diffraction-limited |
| Full frame 45 MP | 4.39 µm | 6.1× | diffraction-limited |
| Full frame 61 MP | 3.79 µm | 7.1× | diffraction-limited |
| APS-C 24 MP | 3.92 µm | 6.9× | diffraction-limited |
| APS-C 40 MP | 3.04 µm | 8.8× | diffraction-limited |
| Micro Four Thirds 20 MP | 3.34 µm | 8.0× | diffraction-limited |
| 1-inch 20 MP | 2.41 µm | 11.1× | diffraction-limited |
| Smartphone 1/1.3" 50 MP | 1.17 µm | 22.9× | diffraction-limited |
f/20 on smaller sensors equals…#
Exposure (brightness) is the same at a given f-number on every format; equivalence describes depth of field and total light.
| Used on | Full-frame equivalent depth of field |
|---|---|
| APS-C (1.5×) | f/30.0 |
| Canon APS-C (1.6×) | f/32.0 |
| Micro Four Thirds (2×) | f/40.0 |
| 1-inch (2.7×) | f/54.0 |
Shutter speed at f/20#
| Light | ISO 100 | ISO 400 | ISO 1600 | ISO 6400 |
|---|---|---|---|---|
| EV 15 · Bright sun, distinct shadows (Sunny 16) | 1/80 s | 1/320 s | 1/1250 s | 1/5000 s |
| EV 13 · Cloudy-bright, no shadows | 1/20 s | 1/80 s | 1/320 s | 1/1250 s |
| EV 12 · Heavy overcast / open shade | 1/10 s | 1/40 s | 1/160 s | 1/640 s |
| EV 10 · Just after sunset | 0.4 s | 1/10 s | 1/40 s | 1/160 s |
| EV 8 · Bright interior, city street at night | 1.6 s | 0.4 s | 1/10 s | 1/40 s |
| EV 5 · Home interior at night | 13 s | 3.2 s | 0.8 s | 1/5 s |
| EV 2 · Distant city lights | 2 min | 25 s | 6 s | 1.6 s |
| EV -2 · Moonlit landscape | > 4 min | > 4 min | 2 min | 25 s |
When to use f/20#
f/20 is a go-to setting for maximum depth of field (macro, focus-free landscapes) and long exposures in daylight, at the cost of diffraction softness.
Other apertures#
Frequently asked questions#
Is f/20 a wide aperture?
No — f/20 is a small (narrow) aperture. Smaller numbers mean larger openings.
How much light does f/20 let in compared to f/2.8?
0.02× (-5.7 stops).
Last updated October 03, 2026 · How we calculate · Sources