The exposure triangle is a practical way to connect aperture, shutter speed and ISO. Aperture and shutter time control captured light. ISO influences image brightness and the way the camera uses the recorded signal. Each setting also brings a trade-off.
One stop means doubling or halving
Changing from 1/250 to 1/500 second halves the recording time: one stop less light. Opening from f/4 to f/2.8 gives about one stop more light. Moving from ISO 400 to 800 is one stop more ISO brightness, with the captured light unchanged if aperture and shutter stay fixed.
Try it
Start with a stationary subject. Shorten the shutter time by one stop, then open the aperture by one stop. Brightness should be similar, but depth of field may change. Repeat with ISO instead and notice which visual qualities change.
By Joseph Hubbard, photographer and artist at Hubbard.ART.
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