Exposure Calculator

Calculate photographic exposure value from aperture, shutter speed, and ISO.

Balance camera settings and see the matching light-level context.

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How This Tool Works

The Exposure Calculator uses the standard EV relationship: EV100 = log2(f-number2 / shutter speed). Choose an aperture, shutter speed, and ISO, and the tool returns the exposure value for those camera settings.

ISO changes the effective exposure requirement: each ISO doubling reduces the needed EV by one stop. The main EV reading is shown at ISO 100 so it can be compared with common exposure-value reference tables.

  • Inputs: Aperture, shutter speed, and ISO.
  • Output: Exposure value with a practical light-level description.
  • Use: Compare equivalent exposure settings or identify the lighting conditions a camera setup fits.

Why This Matters

Exposure value makes the exposure triangle easier to reason about because one EV step represents one stop of light. You can keep the same exposure by opening the aperture and speeding up the shutter, or by closing the aperture and slowing the shutter.

This is useful when balancing motion blur, depth of field, and sensor sensitivity while keeping the overall exposure consistent.

Common Mistakes to Avoid

  • Do not treat ISO as more light: Raising ISO changes sensitivity, not the light reaching the sensor.
  • Check shutter units: Values like 1/125 are fractions of a second, while 2s and 30s are full seconds.
  • Use EV as a guide: Real scenes still depend on metering mode, subject reflectance, and the creative result you want.

Frequently Asked Questions

Common questions about the Exposure Calculator

The exposure triangle balances aperture (f-stop), shutter speed, and ISO. Opening aperture 1 stop doubles light; halving shutter speed doubles light; doubling ISO doubles sensitivity. All three must balance for proper exposure.
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Sources & References

International System of Units (SI): luminous intensity and illuminance

Luminous intensity and illuminance is measured in the candela (cd) and lux (lx). Conversions between SI and other units use exact, internationally agreed factors maintained by NIST.
→Source: NIST — International System of Units (SI)

International System of Units (SI)

Authoritative definitions for luminous intensity and illuminance, from the BIPM SI Brochure (9th edition), the defining reference for the SI.
→Source: BIPM — SI Brochure (9th ed.)

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