20
Concepts in Photography
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 lm or digital image sensor 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 oset
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, aperture can control the depth of eld,
and ISO sensitivity can control the graininess of a photo.
Settings Results
Aperture
value
Wide aperture
= more light
Narrow aperture
= less light
Wide = shallow depth of eld
Narrow = deep depth of eld
Settings Results
Shutter speed
Fast speed
= less light
Slow speed
= more light
Fast = still
Slow = blurry
ISO sensitivity
High sensitivity
= more sensitive to light
Low sensitivity
= less sensitive to light
High = more grainy
Low = less grainy
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