Concepts in Photography
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How the aperture setting, shutter speed, and ISO sensitivity control exposure
The aperture setting, shutter speed, and ISO sensitivity are closely interconnected in
photography. The aperture setting controls the opening that regulates the light that enters
the camera, while the shutter speed determines the length of time that light is allowed to
enter. ISO sensitivity determines the speed at which the film reacts to light. Together, these
three aspects are described as the triangle of exposure.
A change in shutter speed, aperture value, or ISO sensitivity can be offset by adjustments to
the others to maintain the amount of light. The results, however, change according to the
settings. For example, shutter speed is useful in expressing movement, the aperture can
control the depth of field, and the ISO sensitivity can control the graininess of a photo.
Aperture value
Setting Result
Wide aperture = more light
Narrow aperture = less light
Wide = small depth of field
Narrow = large depth of field