f/1.8
Aperture
1.7
Stops less light than f/1
30.86%
Light vs f/1
38.4 cm
DoF: 50 mm at 3 m (FF)
2.4 µm
Airy disk diameter
Depth of field at f/1.8 (full frame)#
| Focal | at 1 m | at 2 m | at 5 m | at 10 m | Hyperfocal |
|---|---|---|---|---|---|
| 16 mm | 43.4 cm | 2.03 m | ∞ | ∞ | 4.76 m |
| 24 mm | 18.5 cm | 76.7 cm | 5.96 m | 149 m | 10.7 m |
| 35 mm | 8.5 cm | 34.9 cm | 2.30 m | 10.9 m | 22.7 m |
| 50 mm | 4.1 cm | 16.9 cm | 1.08 m | 4.51 m | 46.3 m |
| 85 mm | 1.4 cm | 5.7 cm | 36.8 cm | 1.49 m | 134 m |
| 135 mm | 0.5 cm | 2.2 cm | 14.4 cm | 58.5 cm | 338 m |
| 200 mm | 0.2 cm | 1.0 cm | 6.5 cm | 26.5 cm | 741 m |
Diffraction at f/1.8#
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 | 0.4× | no visible loss |
| Full frame 45 MP | 4.39 µm | 0.5× | no visible loss |
| Full frame 61 MP | 3.79 µm | 0.6× | no visible loss |
| APS-C 24 MP | 3.92 µm | 0.6× | no visible loss |
| APS-C 40 MP | 3.04 µm | 0.8× | no visible loss |
| Micro Four Thirds 20 MP | 3.34 µm | 0.7× | no visible loss |
| 1-inch 20 MP | 2.41 µm | 1.0× | no visible loss |
| Smartphone 1/1.3" 50 MP | 1.17 µm | 2.1× | slight softening |
f/1.8 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/2.7 |
| Canon APS-C (1.6×) | f/2.9 |
| Micro Four Thirds (2×) | f/3.6 |
| 1-inch (2.7×) | f/4.9 |
Shutter speed at f/1.8#
| Light | ISO 100 | ISO 400 | ISO 1600 | ISO 6400 |
|---|---|---|---|---|
| EV 15 · Bright sun, distinct shadows (Sunny 16) | too bright | too bright | too bright | too bright |
| EV 13 · Cloudy-bright, no shadows | 1/2500 s | too bright | too bright | too bright |
| EV 12 · Heavy overcast / open shade | 1/1250 s | 1/5000 s | too bright | too bright |
| EV 10 · Just after sunset | 1/320 s | 1/1250 s | 1/5000 s | too bright |
| EV 8 · Bright interior, city street at night | 1/80 s | 1/320 s | 1/1250 s | 1/5000 s |
| EV 5 · Home interior at night | 1/10 s | 1/40 s | 1/160 s | 1/640 s |
| EV 2 · Distant city lights | 0.8 s | 1/5 s | 1/20 s | 1/80 s |
| EV -2 · Moonlit landscape | 13 s | 3.2 s | 0.8 s | 1/5 s |
When to use f/1.8#
f/1.8 is a go-to setting for low light, shallow depth of field, creamy bokeh and subject isolation — the classic portrait and night-street aperture.
Detailed depth-of-field tables#
Other apertures#
Frequently asked questions#
Is f/1.8 a wide aperture?
Yes — f/1.8 is a wide (fast) aperture that lets in lots of light. Smaller numbers mean larger openings.
How much light does f/1.8 let in compared to f/2.8?
2.42× (+1.3 stops).
Last updated October 03, 2026 · How we calculate · Sources