Equivalent Exposure Calculator
Aperture, shutter speed and sensitivity all control how bright a photo is. When you change the aperture, this shows the shutter speed that keeps the light the same.
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- Works offline after your first visit
- Saves on this device
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How it works
The light reaching the sensor depends on the aperture and on time. To keep the same brightness, the time must change by the square of the aperture change.
Moving to a narrower opening, which means a larger f-number, needs a longer shutter time. Moving to a wider opening needs a shorter one.
Worked example
Starting at f/5.6 and 1 over 125 second, the same brightness at f/8 needs about 1 over 61 second.
Questions
Does this keep ISO the same?
Yes. The math holds ISO fixed. Change ISO and the brightness changes too, so use the same ISO as your first setting.
Why does each stop double the time?
A full stop of aperture lets in half or double the light. Shutter speeds follow the same steps, so each full stop matches one step of time.
Is the shutter time exact?
It is a standard calculation, but cameras round to their own speed steps. Pick the closest speed your camera shows.
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