Canon PowerShot A400 Quick Start Manual page 138

Photo Tips and Information
I
The ISO speed is the numeric representation of the
camera's sensitivity to light. The higher the ISO
speed, the higher the sensitivity. A high ISO speed
allows you to shoot images in dark indoor or
outdoor conditions without a flash and also helps
prevent blurred images due to camera shake. This
is convenient when shooting images in places
where flash photography is prohibited. The ISO
speed setting makes full use of the available light,
resulting in images that convey the feel of the place
they were shot.
ISO 50 equivalent ISO 400 equivalent
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