Exposure Value Calculator
Convert aperture, shutter speed and ISO into a single exposure value (EV) — and see the lighting condition it corresponds to.
How it works
EV₁₀₀ = log₂(N² ÷ t) · EV = EV₁₀₀ + log₂(ISO ÷ 100), where N is the f-number and t the shutter time in seconds
Exposure value packs aperture and shutter speed into one number: every whole EV step is a doubling or halving of the light reaching the sensor, the same size as one "stop." The base figure, EV₁₀₀, is measured at ISO 100; raising the ISO adds log₂(ISO ÷ 100) because a more sensitive sensor needs less light for the same result. Photographers use EV to compare exposures and to translate a light meter reading into a lighting condition — EV₁₀₀ 15 is the classic bright-sun "Sunny 16" rule, while a dim living room sits nearer EV 5–7.
Worked example
At f/8, 1/125 s (0.008 s) and ISO 100: EV₁₀₀ = log₂(8² ÷ 0.008) = log₂(8,000) ≈ 13.0. Because ISO is 100, the ISO term is log₂(1) = 0, so the EV is also 13.0 — a cloudy-bright day with no hard shadows.
Frequently asked questions
What is one EV worth?
One exposure value equals one stop — a doubling or halving of light. Going from f/8 to f/11, or from 1/125 s to 1/250 s, each changes the exposure by one EV.
Why does ISO appear in the formula?
EV₁₀₀ describes the light itself at ISO 100. Raising ISO makes the sensor more sensitive, so the same scene reaches a correct exposure at a higher EV — the log₂(ISO ÷ 100) term accounts for that shift.
How does EV relate to the "Sunny 16" rule?
Sunny 16 says that in bright sun you can shoot at f/16 with a shutter of 1/ISO. That corresponds to about EV₁₀₀ 15, which this calculator labels as bright sunlight.
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This calculator is for educational purposes. Double-check important results before acting on them.