20mm f/1.8 depth of field
On a full-frame camera, a 20 mm lens at f/1.8 focused at 3 m (9.84 ft) is sharp from 2.14 m to 5.02 m (2.88 m deep). Hyperfocal distance: 7.43 m (24.4 ft).
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Leave empty to use the standard value for the sensor. Halve it for pixel-level sharpness.
With a 20 mm lens at f/1.8 on full frame focused at 3.00 m, everything from 2.14 m to 5.02 m is acceptably sharp: 2.88 m of depth of field.
- In front of subject
- 86 cm (30%)
- Behind subject
- 2.02 m (70%)
- Hyperfocal distance
- 7.43 m
- Circle of confusion
- 0.030 mm
Fast wide prime for night skies
A 20 mm f/1.8 gathers enough light for clean Milky Way exposures of about 10 seconds at moderate ISO. Focused at infinity, the near limit sits around 7 m, so anything closer will be soft.
Focusing at the hyperfocal distance (about 7.4 m) brings the near limit to under 4 m while keeping stars acceptably sharp; for a close foreground, take a separate frame focused on it.
20mm f/1.8 depth of field table (full frame)
| Focus distance | Near limit | Far limit | Depth of field |
|---|---|---|---|
| 50 cm1.64 ft | 47 cm1.54 ft | 53 cm1.75 ft | 6.5 cm2.6 in |
| 1.00 m3.28 ft | 88 cm2.90 ft | 1.15 m3.78 ft | 27 cm10.6 in |
| 2.00 m6.56 ft | 1.58 m5.18 ft | 2.73 m8.96 ft | 1.15 m3.78 ft |
| 3.00 m9.84 ft | 2.14 m7.02 ft | 5.02 m16.5 ft | 2.88 m9.45 ft |
| 5.00 m16.4 ft | 2.99 m9.81 ft | 15.3 m50.1 ft | 12.3 m40.2 ft |
| 7.50 m24.6 ft | 3.73 m12.2 ft | ∞ | ∞ |
The same lens on other sensors (focused at 3 m)
Same lens, same distance — smaller sensors frame tighter and use a smaller circle of confusion.
| Sensor | Frames like | Near limit | Far limit | Depth of field |
|---|---|---|---|---|
| Full frame | 20 mm | 2.14 m | 5.02 m | 2.88 m |
| APS-C (1.5×) | 31 mm | 2.37 m | 4.10 m | 1.73 m |
| Canon APS-C (1.6×) | 32 mm | 2.39 m | 4.03 m | 1.63 m |
| Micro Four Thirds | 40 mm | 2.50 m | 3.76 m | 1.26 m |
| 1-inch | 55 mm | 2.61 m | 3.52 m | 90 cm |
| Medium format (44×33) | 16 mm | 1.99 m | 6.12 m | 4.13 m |
Hyperfocal distance at other apertures
| Aperture | Full frame | APS-C (1.5×) | Micro Four Thirds |
|---|---|---|---|
| f/2 | 6.69 m | 10.0 m | 13.4 m |
| f/2.8 | 4.78 m | 7.16 m | 9.54 m |
| f/4 | 3.35 m | 5.02 m | 6.69 m |
| f/5.6 | 2.40 m | 3.59 m | 4.78 m |
| f/8 | 1.69 m | 2.52 m | 3.35 m |
| f/11 | 1.23 m | 1.84 m | 2.44 m |
| f/16 | 85 cm | 1.27 m | 1.69 m |
FAQ
How much depth of field does a 20mm f/1.8 lens have?
On full frame, focused at 3 m, the sharp zone runs from 2.14 m to 5.02 m (2.88 m deep). At 1 m it is 27 cm. Depth of field grows roughly with the square of the distance.
What is the hyperfocal distance of a 20mm lens at f/1.8?
7.43 m (24.4 ft) on full frame (c = 0.030 mm) and 11.1 m (36.5 ft) on APS-C. Focus there and everything from half that distance to infinity is acceptably sharp.
Is depth of field different with 20mm f/1.8 on an APS-C camera?
With the same lens at the same distance, APS-C gives slightly less depth of field (1.73 m at 3 m) because of its smaller circle of confusion — but it frames like a 31 mm lens. To match the full-frame framing you would step back, which increases depth of field.
Related lenses
- 14 mm f/2.8Ultra-wide astro and architecture
- 16 mm f/8Landscapes with a strong foreground
- 24 mm f/1.4Astro and environmental portraits
- 24 mm f/8Travel and landscape
- 28 mm f/5.6Zone focusing for street photography
Learn how aperture, distance and focal length interact in depth of field explained.