Calculate exposure

Solve one missing aperture, shutter time, or ISO value while keeping the other two exposure inputs fixed.

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ToolExposure Calculator
Input
Output
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Preview

How it works

The exposure relationship keeps aperture area proportional to shutter time and ISO, so the missing setting is solved from the other two using stops. Aperture is an f-number, shutter is seconds, and ISO is a relative sensitivity scale.

  • Exactly one field is blank.
  • No scene meter or reciprocity model is included.

Worked example

Sunny 16 at ISO 100
EV 15 with aperture set to f/16 and ISO 100, shutter speed left blank
Input
											Ev: 15
Aperture: 16
ISO: 100
Output
												Ev: 15
Aperture: 16
Shutter speed s: 0.0078
ISO: 100

When to use this

Photographers balance shutter against aperture, film exercises convert ISO, and camera lessons demonstrate equivalent settings.

Edge cases

  • Doubling shutter time is one stop, while doubling f-number is not one stop because area follows the square.
  • Slow shutter time can blur motion even when exposure matches.
  • Digital ISO is not identical to film sensitivity or dynamic range.