f/18
Aperture
8.3
Stops less light than f/1
0.31%
Light vs f/1
6.44 m
DoF: 50 mm at 3 m (FF)
24.2 µm
Airy disk diameter
Depth of field at f/18 (full frame)#
| Focal | at 1 m | at 2 m | at 5 m | at 10 m | Hyperfocal |
|---|---|---|---|---|---|
| 16 mm | ∞ | ∞ | ∞ | ∞ | 49.0 cm |
| 24 mm | 11.2 m | ∞ | ∞ | ∞ | 1.09 m |
| 35 mm | 1.04 m | 13.9 m | ∞ | ∞ | 2.30 m |
| 50 mm | 42.8 cm | 2.05 m | ∞ | ∞ | 4.68 m |
| 85 mm | 13.7 cm | 58.4 cm | 4.25 m | 32.9 m | 13.5 m |
| 135 mm | 5.1 cm | 22.2 cm | 1.47 m | 6.39 m | 33.9 m |
| 200 mm | 2.2 cm | 9.7 cm | 65.1 cm | 2.69 m | 74.3 m |
Diffraction at f/18#
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 | 4.0× | diffraction-limited |
| Full frame 45 MP | 4.39 µm | 5.5× | diffraction-limited |
| Full frame 61 MP | 3.79 µm | 6.4× | diffraction-limited |
| APS-C 24 MP | 3.92 µm | 6.2× | diffraction-limited |
| APS-C 40 MP | 3.04 µm | 7.9× | diffraction-limited |
| Micro Four Thirds 20 MP | 3.34 µm | 7.2× | diffraction-limited |
| 1-inch 20 MP | 2.41 µm | 10.0× | diffraction-limited |
| Smartphone 1/1.3" 50 MP | 1.17 µm | 20.6× | diffraction-limited |
f/18 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/27.0 |
| Canon APS-C (1.6×) | f/28.8 |
| Micro Four Thirds (2×) | f/36.0 |
| 1-inch (2.7×) | f/48.6 |
Shutter speed at f/18#
| Light | ISO 100 | ISO 400 | ISO 1600 | ISO 6400 |
|---|---|---|---|---|
| EV 15 · Bright sun, distinct shadows (Sunny 16) | 1/100 s | 1/400 s | 1/1600 s | 1/6400 s |
| EV 13 · Cloudy-bright, no shadows | 1/25 s | 1/100 s | 1/400 s | 1/1600 s |
| EV 12 · Heavy overcast / open shade | 1/13 s | 1/50 s | 1/200 s | 1/800 s |
| EV 10 · Just after sunset | 0.3 s | 1/13 s | 1/50 s | 1/200 s |
| EV 8 · Bright interior, city street at night | 1.3 s | 0.3 s | 1/13 s | 1/50 s |
| EV 5 · Home interior at night | 10 s | 2.5 s | 0.6 s | 1/6 s |
| EV 2 · Distant city lights | 1 min | 20 s | 5 s | 1.3 s |
| EV -2 · Moonlit landscape | > 4 min | > 4 min | 1 min | 20 s |
When to use f/18#
f/18 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/18 a wide aperture?
No — f/18 is a small (narrow) aperture. Smaller numbers mean larger openings.
How much light does f/18 let in compared to f/2.8?
0.02× (-5.4 stops).
Last updated October 03, 2026 · How we calculate · Sources