Light Meter EV to Settings Calculator
Convert an exposure value (EV) into a real shutter speed for your chosen aperture and ISO — plus the approximate scene brightness in lux.
How it works
EV at ISO = EV₁₀₀ + log₂(ISO ÷ 100) · Shutter t = f-number² ÷ 2^EV · Lux ≈ 2.5 × 2^EV₁₀₀
Exposure value is a single number that combines aperture and shutter speed: EV equals the base-2 logarithm of the aperture squared divided by the shutter time, defined at ISO 100. Given a metered EV and the aperture you want, the shutter speed drops straight out of that definition. Raising ISO makes the sensor more sensitive, which is the same as adding EV, so the ISO term is folded in first. The lux figure uses the standard EV-to-illuminance constant to translate the abstract number back into how bright the scene really is.
Worked example
At EV 12, ISO 100 and f/8, the shutter is 8² ÷ 2¹² = 64 ÷ 4096 = 1/64 s. Bump ISO to 400 (two stops) and EV effectively rises to 14, cutting the shutter to 1/256 s.
Sources: Exposure value (Wikipedia)
Frequently asked questions
What EV matches common scenes?
Roughly: EV 15 is bright sun on sand or snow, EV 14 is hazy sun, EV 12 is heavy overcast, EV 8–10 is a bright interior, and EV 3–5 is a dim living room at night. A handheld or phone meter reads it directly.
Why does ISO shift the EV?
EV is defined at ISO 100. Doubling the ISO makes the sensor twice as sensitive, equivalent to one more EV of light, so the working EV is the metered value plus log base 2 of the ISO ratio.
How accurate is the lux estimate?
It uses the widely quoted constant of 2.5 lux at EV 0 (ISO 100), which is a good approximation for reflected-light situations. Precise lux depends on the meter’s calibration constant, so treat it as a guide, not a lab reading.
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This calculator is for educational purposes. Double-check important results before acting on them.