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Photography Exposure Equivalence Calculator

Free · No sign-up

Adjust shutter time to preserve nominal exposure when aperture and ISO change.

Your result

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Enter your values and select calculate.

Next steps

Choose a related calculation for your next question. Enter your values on the next page.

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On this page How it works & practical examples

How to use the Photography Exposure Equivalence Calculator

Assume the scene lighting stays unchanged. The result balances aperture area, shutter duration and ISO scaling, using the entered numerical f-numbers.

The calculation

New shutter seconds = old seconds × (new f/old f)² × old ISO/new ISO

Worked example

1/100 s at f/4 ISO 100 is nominally equivalent to 0.0098 s at f/5.6 ISO 200.

Assumptions and limits

Does not predict image quality, motion blur, depth of field or camera clipping. Lens transmission and camera ISO behavior can differ from this nominal exposure model.

Common questions

Which inputs should I use?