Exposure compensation is used to alter the camera's standard exposure setting. You can make the image look lighter (increased exposure) or darker (decreased exposure). The exposure compensation amount can be set up to +/-2 stops in 1/2-stop increments.
Turn the Mode Dial to any Creative Zone mode except <M>.
Focus the subject and check the exposure level.
Press the shutter button halfway and check the exposure level indicator.
Set the exposure compensation amount.
Turn the <> switch to <ON>, then look at the viewfinder or LCD panel and turn the <> dial to set the desired exposure compensation amount.
Turn the <> dial while pressing the shutter button halfway or within 4 sec. after pressing and releasing the shutter button halfway.
"+" indicates increased exposure, and "- " indicates decreased exposure.
To cancel the exposure compensation, set the exposure compensation amount to <> or <>.
The exposure compensation amount will remain in effect even after you turn the <> switch to <OFF>.
If the standard exposure setting is 1/125 sec. and f/5.6, setting the exposure compensation amount to plus or minus one stop will be the same as setting the shutter speed or aperture as follows:
To prevent the <> dial from turning inadvertently and changing the exposure compensation amount, set the <> switch to <OFF>.
C.Fn-06-1, enables the exposure compensation amount to be set in 1/3-stop increments.
With C.Fn-13-3, you can hold down the < > button and turn the < > dial to set the exposure compensation amount.
> switch to <ON>, then look at the viewfinder or LCD panel and turn the <
> dial to set the desired exposure compensation amount. 
> or <
>.