17
Concepts in Photography
ISO sensitivity
The exposure of an image is determined by the sensitivity of the
camera. This sensitivity is based on international film standards, known
as ISO standards. On digital cameras, this sensitivity rating is used
to represent the sensitivity of the digital mechanism that captures the
image.
ISO sensitivity doubles as the number doubles. For example, an
ISO 200 setting is capable of capturing images at twice the speed of an
ISO 100 setting. However, higher ISO settings can result in “noise”—
small specks, spots, and other phenomena in a photo that give the shot
a noisy or dirty appearance. As a general rule, it is best to use a low
ISO setting to prevent noise in your photos, unless you are shooting in
darkened environments or at night.
Changes in the quality and brightness according to ISO sensitivity
Because a low ISO sensitivity means the camera will be less sensitive
to light, you need more light to have an optimal exposure. When using
a low ISO sensitivity, open the aperture more or reduce the shutter
speed to allow more light to enter the camera. For example, on a sunny
day when light is abundant, a low ISO sensitivity does not require a low
shutter speed. However, in a dark place or at night, a low ISO sensitivity
and a fast shutter speed will result in a blurry photo.
A photo captured with a tripod and
high sensitivity
A blurred photo with a low ISO sensitivity
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