By Zencalcy Editorial TeamLast reviewed About us
Exposure value bundles aperture and shutter speed into a single number at a given ISO. Doubling the shutter time or opening the aperture by one stop changes EV by one, which is why the exposure triangle is easy to balance once you think in stops.
Exposure value from aperture, shutter speed and ISO.
EV = log₂(N² / t) − log₂(ISO / 100)
N is the f-number, t the shutter time in seconds and ISO the sensitivity. The ISO term shifts the EV scale so that ISO 100 is the reference.
| Symbol | Meaning |
|---|---|
| EV | Exposure value at the stated ISO. |
| N | f-number of the lens aperture. |
| t | Shutter time in seconds. |
| ISO | Sensor sensitivity, 100 at the reference. |
N²/t = 64 × 125 = 8000, and log₂ 8000 = 12.97, so EV ≈ 13. At ISO 400 the same settings would be EV 11.
Continue with the Coherence Length Calculator, Critical Angle Calculator, or the Depth of Field Calculator — or browse more optics and light tools and all physics calculators.
A factor of two in exposure. You can trade one stop of aperture for one stop of shutter time or ISO without changing brightness.
Results are computed from the standard equations of classical mechanics. Unit conversions use the SI definitions published by NIST. Air resistance is ignored unless the calculator names a drag model.
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Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026