Exposure value is a single number that sums up how much light a combination of camera settings lets in. Each step of 1 EV halves or doubles the light, so f/8 at 1/250 s and f/5.6 at 1/500 s share the same EV – they are equivalent exposures. Photographers use EV to describe scenes (bright sun is about EV 15 at ISO 100, a lit living room about EV 5–6) and light meters use it to suggest settings.
There are two closely related figures. The settings EV, log₂(N²/t), depends only on aperture and shutter speed. The scene EV at ISO 100 also takes the ISO into account: raising the ISO by one stop lets you shoot one EV darker scene with the same aperture and shutter. This calculator reports both, together with an approximate incident light level in lux.
Use it to check that a set of settings fits a scene, to translate the Sunny 16 rule to your camera, or to solve for the one setting you have not decided – for example the ISO needed for f/2.8 and 1/250 s at an indoor sports event (about EV 7).
How to use the Exposure Value Calculator
- Calculate
- Aperture — Marked f-numbers are rounded; the calculator uses the exact values (f/22 is really f/22.63).
- f-number (N)
- Shutter speed
- Exposure time
- ISO sensitivity
- ISO value
- Exposure value of the scene (EV at ISO 100)
Everything is calculated in your browser, so results appear instantly and nothing you type is sent to a server.
How it works
Choose what to calculate. In the first mode the EV follows from your aperture, shutter speed and ISO; in the others the calculator rearranges the same formula to give the missing setting and rounds it to the nearest standard third-stop value.
Worked example
An evening street shot at f/5.6 (exact 5.657), 1/125 s and ISO 400:
EV₁₀₀ = log₂(100 × 5.657² ÷ (400 × 1/125)) = log₂(100 × 32 × 125 ÷ 400) = log₂(1000) ≈ 9.97, so about EV 10 – the light just after sunset. The settings EV alone is log₂(32 × 125) = 11.97. To shoot the same scene at f/2.8 and 1/125 s you need ISO 100 × 8 × 125 ÷ 2^9.97 ≈ 100.
Exposure value chart (ISO 100)
| EV | Typical scene | Example settings |
|---|---|---|
| −6 | Starlight only | f/1.4, 128 s |
| −3 | Full-moon landscape | f/2.8, 64 s |
| 3 | Fireworks | f/8, 8 s |
| 6 | Bright home interior | f/2, 1/15 s |
| 9 | Neon signs, dusk | f/2.8, 1/60 s |
| 12 | Open shade, overcast | f/5.6, 1/125 s |
| 15 | Bright sun | f/16, 1/125 s |
| 16 | Sun on snow or sand | f/16, 1/250 s |
Formula
EV₁₀₀ = log₂(100 · N² ÷ (ISO · t)) · settings EV = log₂(N² ÷ t) · N = √(2^EV · ISO · t ÷ 100) · t = 100 · N² ÷ (ISO · 2^EV) · ISO = 100 · N² ÷ (t · 2^EV) · illuminance ≈ 2.5 · 2^EV₁₀₀ lux
Worked example
Inputs — Calculate: Exposure value (EV) from my settings; Aperture: f/5.6; Shutter speed: 1/125 s; ISO sensitivity: ISO 400.
Results — Exposure value (EV at ISO 100) = 9.97; Setting to use = EV 10; Rounded EV = 10; Typical lighting at this EV = EV 10 – Landscapes just after sunset; Settings EV, log₂(N²/t), ignoring ISO = 11.97; Focal ratio (exact) = 5.657.
Key terms
- Exposure value (EV)
- log₂ of N²/t, a single number for equivalent aperture and shutter combinations.
- Stop
- A doubling or halving of light; 1 EV.
- ISO
- Sensitivity setting; doubling it allows one stop less light.
- Sunny 16 rule
- In bright sun, f/16 with a shutter time of 1/ISO gives a correct exposure.
Frequently asked questions
What is a good EV for daylight?
Bright sun on a clear day is about EV 15 at ISO 100; overcast skies are EV 12–13 and open shade about EV 12.
Is a higher EV brighter or darker?
A higher scene EV means more light. A higher settings EV means less light reaches the sensor (smaller aperture or faster shutter).
Do f/8 at 1/250 s and f/5.6 at 1/500 s give the same exposure?
Yes – both are EV 14 (settings EV). One stop wider aperture is balanced by one stop faster shutter.
How does ISO change the EV?
Each doubling of ISO lets you shoot a scene one EV darker with the same aperture and shutter speed.
What is EV 0?
f/1 at 1 second (or f/1.4 at 2 s) at ISO 100 – roughly dim indoor lighting.
Why does my camera say "EV +1"?
That is exposure compensation – a deliberate one-stop brightening relative to the meter, not the scene EV.
How accurate is the lux estimate?
It uses the standard incident-meter constant (C = 250), so it is good to roughly ±30% – fine for planning.