What the exposure calculator does
Exposure is set by three controls — aperture, shutter speed and ISO — and any combination that admits the same light gives the same brightness. This calculator takes an aperture, a shutter speed and an ISO and returns the exposure value (EV), the single number that describes that light level, so you can find equivalent settings: the shutter speed you need after opening up two stops, or the ISO that lets you hand-hold a lens in the same light. Runs in your browser.
The formulas
EV₁₀₀ = log₂( N² ÷ t ) N = f-number, t = shutter time in seconds, at ISO 100
EV at other ISO = EV₁₀₀ + log₂( ISO ÷ 100 )
f/5.6, 1/250 s, ISO 100: EV = log₂(31.36 ÷ 0.004) = log₂(7,840) = 12.9 ≈ EV 13
Same light at ISO 400: EV 13 + 2 = EV 15 available — two stops faster shutter or smaller apertureEach whole EV is one stop — double or half the light. Higher EV means brighter conditions (or more sensitivity). Settings that share an EV are interchangeable for brightness; they differ in depth of field, motion blur and noise.
Typical scenes and their EV at ISO 100
| EV | Scene | Example setting |
|---|---|---|
| 16 | Bright sun on snow or sand | f/16, 1/1000 |
| 15 | Full sunlight — the 'Sunny 16' rule | f/16, 1/125 |
| 13 | Hazy sun, light overcast | f/8, 1/250 |
| 12 | Overcast, open shade | f/5.6, 1/250 |
| 9–10 | Sunset, bright interiors, sports venues | f/4, 1/60 |
| 7 | Well-lit interiors, city street at night | f/2.8, 1/15 |
| 5 | Dim interiors, candle-lit table | f/2, 1/4 |
| 2 | Night street lighting | f/2, 2 s |
| −3 to −6 | Moonlight, milky way | f/2.8, 30 s at ISO 3200+ |
The stop scales
| Aperture (each = 1 stop) | Shutter (s) | ISO |
|---|---|---|
| f/1.4 | 1/1000 | 100 |
| f/2 | 1/500 | 200 |
| f/2.8 | 1/250 | 400 |
| f/4 | 1/125 | 800 |
| f/5.6 | 1/60 | 1600 |
| f/8 | 1/30 | 3200 |
| f/11 | 1/15 | 6400 |
| f/16 | 1/8 | 12800 |
Move one column down for one stop less light, one row up for one stop more. Cameras also offer third-stop steps between these values.
Choosing between equivalent settings
- Aperture controls depth of field: wide for isolation, small for front-to-back sharpness (see the Depth of Field Calculator).
- Shutter speed controls motion: 1/500 or faster freezes people, 1/1000+ for sport and birds; slow speeds blur water and traffic. Hand-holding needs about 1/focal length (equivalent) or faster without stabilisation.
- ISO controls noise: keep it as low as the other two allow. Modern sensors are clean to ISO 1600–3200 on full frame; raise it before accepting a blurred shot.
- Neutral density filters subtract stops (ND8 = 3 stops), letting you use wide apertures or long exposures in bright light — the calculator shows what the new shutter speed must be.
Common uses
- Working out settings for a manual-only camera or a film camera without a meter, from the scene table.
- Translating a setting you know works into an equivalent with the aperture or shutter speed you want.
- Planning long exposures with ND filters.
- Comparing the light level of two locations or two times of day.
- Understanding what “EV compensation” on the camera is adjusting.