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Exposure Value, Aperture & ISO Shutter Time

Estimate shutter duration from EV at ISO 100, aperture and ISO, using retained scene and camera-setting presets or custom values.

Calculator inputs

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Enter the known values in the units shown. Results update as you type.
Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
Use the worked example to check the method. Reset restores the starting fields.

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

At EV 15, f/8 and ISO 100, the model gives 1/512 second. Choose an available camera setting close to the calculated duration.

Exposure time in seconds = 100 × f-number² / (ISO × 2^EV₁₀₀)

Enter these known values and leave the other values blank.

Scene presets are rough lighting examples, not measurements. Use a meter or a supplied EV at ISO 100 when available.
Aperture presets use the captured stop-series values behind their rounded f-number labels. Custom aperture and ISO values must be positive; ISO values below 100 are supported.
The retained custom EV range is −20 to 24. The formula assumes the usual exposure-value relationship and omits lens transmission, filters and film reciprocity failure.
The calculated exposure does not guarantee motion freezing, sharpness or correct highlights. Hardware shutter increments may require rounding and a test exposure.

The formula produces a mathematical duration. Cameras offer discrete nominal settings; use the nearest suitable setting and check the exposure.

Bookify accepts any positive custom ISO sensitivity, including values below 100, while retaining the exposure equation and scene presets.