Canon EOS Rebel XS Instruction Manual page 57

BSO: Changing the ISO Speed* _y_
Set the ISO speed (image sensor's sensitivity to light) to suit the
ambient light level. In the Basic Zone modes, the ISO speed is set
automatically.
Press the <IS0> button. (G6)
};_[Iso speed] will appear.
'_} Select the ISO speed.
_ Turn the <;eft> dial or press the
<_V> key to select the ISO speed.
_ You can also look at the ISO speed in
the viewfinder while turning the
< ;_:%> dial
ISO Speed Guide
100/200 Sunny outdoors
400/800 Overcast skies, evening
1600 Night or dark indoors
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The higher the ISO speed, the
farther the flash range will be
(p88)
About Auto _SO
This mode sets the ISO speed automatically between ISO 100 - 800 to
suit the shooting mode and ambient light level. For flash and < M >
(manual) exposures, ISO 400 is set. When you press the shutter button
halfway, the automatically-set ISO speed is displayed in the viewfinder
and on the LCD monitor.
@ Using 8 high _SO Speed or shooting in high-temperature conditions may
result in more grainy images. Long exposures can also cause irregular
colors in the image.
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