I'm trying to help someone with a Canon XSi. I'm not used to the Canons that use menus (rather than buttons on the body).
Does anyone know how to set up the Canon XSi to take a bracketed exposure of 3 photos? -1, 0, and +1?
The Canon 450D/XSi has the ability to automatically bracket exposures +/- 3.0 EV, in 0.5 or 0.3 EV increments. To get to the AEB menu you have to have another thing setup correctly. It is displayed only in the P, TV, Av, M or A-DEP modes, not in any of the 'Basic Zone' modes (such as full Auto or the Scene modes). Once you have that setup, hit the Menu button on the back and scroll over right to the second option in the menu, and you will see the first option is "AEB". Select that and you can expand the selection using the right and left arrows up to a full +/- 3 depending on what you would like. In your particular case you would expand it to -1,0,and +1 to get the desired effect you asked for.
At this point when you start shooting images it will take a series of three images for the bracketing. It is usually a benefit to put the camera into a continuous shooting mode for faster shots at this point, but that is a preference.
The website dpreview does have images of the menu if you would like a visual of that screen here.