Exposure Value Calculator: EV and Equivalent Exposure
This exposure value calculator works out the EV from your aperture, shutter speed and ISO and shows which shutter speed gives the same exposure at every other aperture.
Example: Aperture: f/8 · Shutter speed: 1/125 · ISO: 100 · New aperture: f/4 · New ISO: 100 → Exposure value: EV 13.0 (ISO 100) – at f/4 and ISO 100: 1/500 s. Source: Wikipedia – Exposure value (EV = log₂(N²/t), equivalent exposures). Updated: .
How it is calculated
An aperture of f/8, 1/125 s and ISO 100 give EV 13: the exposure value combines aperture and shutter speed in one number. The same EV means the same exposure, even with a different combination.
How it is calculated
The exposure value is EV = log₂(N² / t) with the f-number N and the time t in seconds, referenced to ISO 100. At a higher ISO the value falls by log₂(ISO / 100). Equal exposure at a new aperture N₂ gives t₂ = t · (N₂ / N)². Opening the aperture by one stop lets you halve the shutter time, and doubling the ISO does the same.
What it is useful for
- Switching between depth of field (aperture) and motion blur (shutter speed) without changing brightness.
- Checking manual exposures from a hand-held meter or the sunny 16 rule.
- Planning with neutral density filters and long exposures.
Frequently asked questions
What is exposure value (EV)?
A number for the amount of light reaching the sensor: EV = log₂(N² / t) at ISO 100. The higher the value, the brighter the scene.
How many stops are there between f/8 and f/4?
Two stops: f/8, f/5.6, f/4. Four times as much light enters, so the shutter time must drop to a quarter.
How do I get the same exposure with a different aperture?
Use t₂ = t · (N₂ / N)². From f/8 to f/4, 1/125 s becomes 1/500 s, for example. The table shows this for every aperture.
Why do the camera’s nominal values differ from the calculated ones?
Cameras show rounded values such as 1/60 or 1/250. The difference is usually under a third of a stop and irrelevant in practice.
Sources and legal basis
As of: · Editorial policy
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