Photography

Exposure value (EV).

Type the aperture, shutter speed and ISO you used. Get the exposure value, the EV100 of the light that exposed correctly, and the shutter speed that gives the same exposure at each full-stop aperture. Runs in your browser; nothing is sent anywhere.

Your numbers

Result

Fill the form and press Calculate.

Worked example

A picture taken at f/8, 1/125 s, ISO 100: EV = log2(8² ÷ (1/125)) = log2(8000) = 12.97. At ISO 100 that is also the EV100. Shoot the same light at ISO 400 and the correct exposure for that light is still EV100 12.97, but the settings you would use give EV 14.97 at ISO 400, two stops higher.

How it works

EV = log2(N² / t), with N the f-number and t the shutter time in seconds, is the exposure value at ISO 100. For another ISO, EV_S = EV₁₀₀ + log2(S / 100). This tool reports the value of your settings as "EV at your ISO" and removes the ISO term to give EV100, the standard way to compare light levels. Each whole EV is one stop. The table solves t = N² × 100 / (ISO × 2^EV100) for each aperture, so every row gives the same exposure.

Exposure value describes the exposure settings and, through the meter equation, the scene light that those settings render at normal brightness. Metering, exposure compensation and a camera’s own calibration can shift the choice you finally make.

Sources and basis (checked 2026-10-05): Wikipedia: Exposure value (EV = log2(N²/t); EV_S = EV₁₀₀ + log2(S/100); ISO 2720 / APEX basis). Arithmetic on the numbers you enter; no data is looked up.

FAQ

What is exposure value (EV)?

EV is a single number for a combination of aperture and shutter speed, defined as log2(N²/t) at ISO 100. Settings with the same EV give the same exposure. One EV step is one stop.

What is EV100?

EV100 is the exposure value referred to ISO 100. It lets you compare light levels on one scale whatever ISO you used: EV100 = EV − log2(ISO/100).

How do I get a shutter speed from EV?

Pick an aperture, then t = N² × 100 / (ISO × 2^EV100). The table on this page does that for each full-stop aperture.

Does a higher EV mean brighter light?

Yes. EV100 rises by one for every doubling of the light, so bright sun sits at a higher EV100 than a dim room.

Why does the tool accept 1/125 as text?

Camera shutter speeds are fractions. Type 1/125, or a plain number of seconds such as 0.5 or 30.