GlenCalc

Exposure value calculator

Enter a correct exposure, then a new aperture and ISO: you get the shutter speed that gives the same exposure.

Your answer

New shutter speed1/2,041 s0.00049 s
Exposure value (EV at ISO 100)14

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How we worked it out

Updated as you change the numbers.

  1. EV = log₂(N² ÷ t) − log₂(ISO ÷ 100). New t = t × (N₂ ÷ N₁)² × (ISO₁ ÷ ISO₂): each stop of aperture or ISO halves or doubles the time.

Method and assumptions

Exposure depends on the light reaching the sensor (aperture area ∝ 1 ÷ N², and time) and the sensor’s sensitivity. EV 15 is roughly bright sun (the “sunny 16” rule: f/16 at 1/ISO).

Questions

What shutter speed at f/2.8 matches f/8 at 1/250?

About 1/2000 s (three stops faster).

Sources

Method and figures checked on . Every worked answer on this page is covered by an automated test. Found a mistake? Tell us.

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