Canon EOS Rebel XS Instruction Manual page 74

Av: Changing the Depth of FieEd
Using the Built-in Flash
To obtain a correct flash exposure, the flash output will be set
automatically to match the set aperture (autoflash exposure). The
shutter speed will be set automatically between 1/200 sec. - 30 sec to
suit the scene's brightness.
In low light, the main subject is exposed with the automatic flash, and
the background is exposed with a slow shutter speed set automatically
Both the subject and background look propedy exposed (automatic
slow-speed flash sync). If you are handholding the camera, keep it
steady to prevent camera shake. Using a tripod is recommended
To prevent slow-speed sync, select the [r_ Custom Functions (C.Fn)]
menu's [Flash sync. speed [r_ Av mode] (p.154) and set it to [1: 1/
200sec. (fixed}].
Depth-of=Field Preview*
Press the depth-of-field preview button
to stop down to the current aperture
setting You can check the depth of field
(range of acceptable focus) through the
viewfinder.
] If it is difficult to discern the depth of field, first set the lowest f-number. Then
hold down the depth-of-field preview button and _ook through the viewfinder
while turning the <_> dial to the right. As the aperture gets sm_[}er, the
viewfinder wi!} g_adua!ly !ook darke_ You can a!so see how the depth of field
74