What is exposure value (EV)?

EV is a single number describing how much light an exposure lets in. It combines aperture and shutter speed: EV equals the base-2 logarithm of the aperture squared divided by the shutter time. Each whole EV step is one stop.

EV100 is the exposure value referenced to ISO 100, the standard used by light meters. To convert an EV measured at another ISO, subtract the base-2 logarithm of that ISO divided by 100.

What are equivalent exposures?

Equivalent exposures are different aperture and shutter combinations that produce the same overall brightness. Opening the aperture one stop and shortening the shutter one stop cancel out, so the image stays equally bright.

Why would I change to an equivalent exposure?

To control creative effect without changing brightness. A wide aperture blurs the background and a fast shutter freezes motion, so you swap between equivalent pairs to get the look you want while keeping correct exposure.

Does changing ISO change the EV?

Raising ISO makes the sensor more sensitive, so the same brightness is reached at a higher EV. The tool shows both the EV at your chosen ISO and the normalized EV100 so you can compare scenes fairly.

Exposure Value (EV) Calculator

Exposure value (EV) reduces the whole exposure triangle to a single number, making it easy to compare scene brightness and swap between equivalent camera settings. This calculator computes EV from any aperture, shutter, and ISO, then lists every aperture and shutter pair that produces the same exposure.

How it works

Exposure value is defined from aperture and shutter speed:

EV = log₂(N² ÷ t)

where N is the f-number and t is the shutter time in seconds. Each whole step of EV equals one stop of light. Because light meters reference ISO 100, the tool normalizes to EV100:

EV₁₀₀ = EV − log₂(ISO ÷ 100)

Raising ISO makes the sensor more sensitive, so the same brightness corresponds to a higher EV — the normalization lets you compare scenes regardless of ISO.

Equivalent exposures

Two settings are equivalent when they let the same total light reach the sensor. Opening the aperture one stop doubles the light, and shortening the shutter one stop halves it, so the two cancel. The tool holds N² ÷ t constant and solves for the shutter time at each standard aperture:

t = N² ÷ 2^EV

Example and tips

A reading of f/8 at 1/250 s and ISO 100 gives EV = log₂(64 × 250) = log₂(16000) ≈ 13.97, essentially EV 14. The equivalent at f/2.8 would be about 1/2000 s — same brightness, but a shallow depth of field and frozen motion. Use the list to trade depth of field against motion blur while keeping the exposure perfect.