That button is to make the flash pop-up, so that you can force the flash to work when you are in one of the creative modes.
See page 54 of your manual.
This is most often used when you want to use "fill flash" when you are photographing a subject when the prevailing light is behind the subject.
You have a mode dial on top of the camera with 12 settings.
One of the end settings is to Turn Off the Flash.
It's icon looks like a lightning bolt with a slash through it.
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I hope someone out there can help me. I have a Canon Rebel XTI Camera and I have been trying to disable the flash. When i press the button that is designated to control the flash, the flash won't turn off. The button I am referring to is the one that looks like the lightening bolt. Any help would be appreciated.
Thank You for your time,
Ginger Pitner

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