Exposure Value Calculator
Work out the exposure value (EV) of any aperture, shutter speed and ISO combination, with equivalent exposures and scene light levels.
Shutter speeds accept 1/125, 0.5 or 30.
- Your settings (EV)
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- The light itself (EV100)
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- Scene luminance
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- Incident light
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- Typical lighting
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EV describes your settings; EV100 describes the scene, with ISO taken back out.
Equivalent exposures
Same amount of light at ISO 100 — open up a stop, halve the time. Tap a shutter speed to load that pair into the calculator.
| Aperture | Shutter speed | Exact seconds |
|---|
* Beyond most cameras' shutter range (faster than 1/32000 s or longer than 1 hour).
How it works
Exposure value is a single number for “how much light a camera setting lets through”. This
calculator uses the standard APEX definition EV = log₂(N² ÷ t), where
N is the f-number and t the shutter speed in seconds. That number
describes the settings only, so f/16 at 1/125 s is EV 15 whatever ISO you dial in. To describe
the scene instead, the ISO is folded back out:
EV₁₀₀ = EV − log₂(ISO ÷ 100). Shooting f/16 at 1/125 s on ISO 400 therefore reads
EV 15 for the settings but EV₁₀₀ 13 for the light — two stops less light than full sun, which
is exactly the “sunny 16” rule in reverse.
From EV₁₀₀ the page also estimates the light itself with the two ISO 2720 reflected- and
incident-light constants: luminance L = 2^EV₁₀₀ × K ÷ 100 with K = 12.5
(so EV₁₀₀ 15 ≈ 4,000 cd/m²) and illuminance E = 2^EV₁₀₀ × C ÷ 100 with C = 250
(≈ 80,000 lux). The equivalent-exposure table then solves the same equation for time —
t = N² ÷ 2^EV — at every full stop from f/1.4 to f/22, so you can trade depth of
field against motion blur without changing the brightness. Everything is plain arithmetic in
your browser: nothing is uploaded, there is no sign-up and there are no ads.
Frequently asked questions
How do you calculate EV from aperture and shutter speed?
Exposure value uses the APEX formula EV = log₂(N² ÷ t), where N is the f-number and t the shutter speed in seconds. For example f/16 at 1/125 s gives log₂(256 × 125) = log₂(32000) ≈ 15. That number describes the settings only, so it does not change when you change ISO.
What is the difference between EV and EV100?
EV describes the camera settings; EV₁₀₀ describes the light in the scene as if you were shooting at ISO 100. The calculator converts between them with EV₁₀₀ = EV − log₂(ISO ÷ 100), so f/16 at 1/125 s on ISO 400 reads EV 15 for the settings but EV₁₀₀ 13 for the light, two stops darker than full sun.
What are equivalent exposures?
Any settings that share the same EV let through the same amount of light: open up one stop of aperture and halve the shutter time. The table on this page solves t = N² ÷ 2^EV for every full stop from f/1.4 to f/22, so you can trade depth of field for motion blur without changing the brightness.