Canon RebelT3i EOS 600D Instruction Manual page 79

ISO : Changing the lSO Speed _
Set the ISO speed (image sensor's sensitivity to light) to suit the
ambient light level. In Basic Zone modes, the ISO speed is set
automatically (p.80).
Press the <ISO> button. (4_6)
_y,, [ISO speed] will appear.
Set the ISO speed.
_ Press the <_> key or turn the
<_> dial to select the desired ISO
speed, then press <__>.
_ You can also set the ISO speed in the
viewfinder while turning the < _ > dial.
_ With [AUTO] selected, the ISO speed
will be set automatically (p.80).
ISO Speed Guide
Iso Sp_ed Shooting situation (NO flash) FlaSh Range
100 - 400 Sunny outdoors The higher the ISO speed,
400 - 1600 Overcast skies or evening time the farther the flash range will
1600 - 6400, H Dark indoors or night extend (p.90).
* High ISO speeds will result in grainier images.
_] Under [_ Custom Functions (C.Fn)], if [2: ISO expansion] is set to [1:
On], "H" (equivalent to ISO 12800) can also be set (p.252).
U
Under [_'-: Custom Functions (C.Fn)], if [6: Highlight tone priority] is
set to [1: Enabte], ISO 100 and "H" (equivalent to ISO 12800)cannot be
selected (p.254).
Shooting in high temperatures may result in images that look grainier.
Long exposures can also cause _rregular colors in the image.
When you shoot at high ISO speeds, noise (banding, dots of light, etc.)
may become noticeable_
79