f/2.5
Aperture
2.6
Stops less light than f/1
16.00%
Light vs f/1
53.5 cm
DoF: 50 mm at 3 m (FF)
3.4 µm
Airy disk diameter
Depth of field at f/2.5 (full frame)#
| Focal | at 1 m | at 2 m | at 5 m | at 10 m | Hyperfocal |
|---|---|---|---|---|---|
| 16 mm | 62.9 cm | 3.51 m | ∞ | ∞ | 3.43 m |
| 24 mm | 25.8 cm | 1.10 m | 11.2 m | ∞ | 7.70 m |
| 35 mm | 11.9 cm | 48.8 cm | 3.35 m | 19.4 m | 16.4 m |
| 50 mm | 5.7 cm | 23.5 cm | 1.52 m | 6.55 m | 33.4 m |
| 85 mm | 1.9 cm | 8.0 cm | 51.2 cm | 2.08 m | 96.4 m |
| 135 mm | 0.7 cm | 3.1 cm | 20.0 cm | 81.3 cm | 243 m |
| 200 mm | 0.3 cm | 1.4 cm | 9.0 cm | 36.8 cm | 534 m |
Diffraction at f/2.5#
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 | 0.6× | no visible loss |
| Full frame 45 MP | 4.39 µm | 0.8× | no visible loss |
| Full frame 61 MP | 3.79 µm | 0.9× | no visible loss |
| APS-C 24 MP | 3.92 µm | 0.9× | no visible loss |
| APS-C 40 MP | 3.04 µm | 1.1× | no visible loss |
| Micro Four Thirds 20 MP | 3.34 µm | 1.0× | no visible loss |
| 1-inch 20 MP | 2.41 µm | 1.4× | no visible loss |
| Smartphone 1/1.3" 50 MP | 1.17 µm | 2.9× | slight softening |
f/2.5 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/3.8 |
| Canon APS-C (1.6×) | f/4.0 |
| Micro Four Thirds (2×) | f/5.0 |
| 1-inch (2.7×) | f/6.8 |
Shutter speed at f/2.5#
| Light | ISO 100 | ISO 400 | ISO 1600 | ISO 6400 |
|---|---|---|---|---|
| EV 15 · Bright sun, distinct shadows (Sunny 16) | 1/5000 s | too bright | too bright | too bright |
| EV 13 · Cloudy-bright, no shadows | 1/1250 s | 1/5000 s | too bright | too bright |
| EV 12 · Heavy overcast / open shade | 1/640 s | 1/2500 s | too bright | too bright |
| EV 10 · Just after sunset | 1/160 s | 1/640 s | 1/2500 s | too bright |
| EV 8 · Bright interior, city street at night | 1/40 s | 1/160 s | 1/640 s | 1/2500 s |
| EV 5 · Home interior at night | 1/5 s | 1/20 s | 1/80 s | 1/320 s |
| EV 2 · Distant city lights | 1.6 s | 0.4 s | 1/10 s | 1/40 s |
| EV -2 · Moonlit landscape | 25 s | 6 s | 1.6 s | 0.4 s |
When to use f/2.5#
f/2.5 is a go-to setting for portraits with some context, events and indoor sport; most zooms are sharpest a stop down from wide open.
Other apertures#
Frequently asked questions#
Is f/2.5 a wide aperture?
Yes — f/2.5 is a wide (fast) aperture that lets in lots of light. Smaller numbers mean larger openings.
How much light does f/2.5 let in compared to f/2.8?
1.25× (+0.3 stops).
Last updated October 03, 2026 · How we calculate · Sources