Canon Rebel T2i EOS 550D Instruction Manual page 63

About "AUTO" for Automatic ISO Speed
Shooting Mode
1/7/3/4/5/6/C
d/s/f/a/8
2
With flash
*1: Depending on the maximum ISO speed that has been set.
*2: If fill flash results in overexposure, ISO 100 or a higher ISO will be set.
*3: In the <d/8> modes and Basic Zone modes <except 6>, ISO 400 -
1600 will be set automatically if bounce flash is used with an external
Speedlite. If the maximum ISO speed has been set to [400] or [800], the ISO
speed will be set within this range.
When "AUTO" is set, the ISO speed will be displayed in whole-stop
increments of 100, 200, 400, 800, 1600, or 3200. However, the actual ISO
speed may be set more precisely. Therefore, in the image's shooting
information, you may find an ISO speed like 125 or 640 displayed as the
ISO speed.
3 Setting the Maximum ISO Speed for Auto ISON
For Auto ISO, you can set the maximum ISO speed within ISO 400 -
6400.
Z: Changing the ISO SpeedN
If the ISO speed is set to "AUTO", the
actual ISO speed to be set will be
displayed when you press the shutter
button halfway. As indicated below, the
ISO speed will be set automatically to
suit the shooting mode.
ISO Speed Setting
Automatically set within ISO 100 - 3200
Automatically set within ISO 100 - 6400
Fixed at ISO 100
*2*3
Fixed at ISO 400
Under the [y] tab, select [ISO Auto],
then press <0>. Select the ISO speed,
then press <0>.
*1
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