Exposure Calculator — ISO, Aperture & Shutter Speed

Mastering the Photography Exposure Triangle

The exposure triangle consists of three interdependent settings that control how much light reaches your camera sensor: ISO (sensor sensitivity), aperture (lens opening size measured in f-stops), and shutter speed (duration of exposure). This calculator helps you find equivalent exposures when changing one setting by adjusting the others to maintain the same overall brightness, following the reciprocity law of photography.

Each setting is measured in stops, where one stop represents a doubling or halving of light. Changing ISO from 100 to 200 doubles sensitivity (one stop brighter). Opening the aperture from f/8 to f/5.6 doubles the light entering the lens (one stop brighter). Slowing the shutter from 1/500s to 1/250s doubles the exposure time (one stop brighter). The calculator applies these relationships so you can see, for example, that an exposure of ISO 100, f/8, 1/250s is equivalent to ISO 400, f/8, 1/1000s or ISO 100, f/4, 1/1000s.

Understanding exposure equivalence is essential for creative photography decisions. A wider aperture (lower f-number) creates shallow depth of field for portrait blur, but requires a faster shutter speed to compensate. A slower shutter speed allows motion blur for artistic waterfall shots, but may require a smaller aperture or lower ISO to avoid overexposure. Sports photographers use high ISO to enable fast shutter speeds in dim stadiums, trading some image noise for the ability to freeze action. This calculator takes the mental math out of these tradeoffs.