On the Canon EOS 450D (Rebel XSi) camera, Liveview mode always shows the true exposure of the image. If exposure is set too dark (fast shutter and closed aperture), Liveview shows a darker image. If exposure is set too bright (slow shutter and open aperture), Liveview shows a brighter image.
However some cameras do have an option to select whether the camera should always show a truly exposed image or, otherwise, always how a normally exposed image.
How do I switch my 450D to the second behavior?