Canon Rebel T5i EOS 700D Instruction Manual page 114

AM : Changing the Depth of Field
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 wiii 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 properly 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 a slow shutter speed, under [_1 : Flash control], set
[Flash sync. speed in Av mode] to [1/200-1/60 sec. auto] or [11200
sec. (fixed)] (p.219).
Depth of FieJd PrevieW_
The aperture opening (diaphragm) changes only at the moment when
the picture is taken. Otherwise, the aperture remains fully open.
Therefore, when you look at the scene through the viewfinder or on the
LCD monitor, the depth of field wiii look narrow.
Press the depth-of-field preview button
to stop down the lens to the current
aperture setting and check the depth of
field (range of acceptable focus).
[] While boking at the Live View image (p]i46)and holding dOWn the depth_of-
field preview button;yo u can change the apertu re and see ho w the depth
field changes,
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