Canon EOS REBEL T5 Instruction Manual page 145

Using AF to Focus (AF Method)
Notes for [FlexiZone - Single] and [uLive mode]
AF Operation
Focusing will take longer than with [Quick mode].
Even when focus has been achieved, pressing the shutter button
halfway will focus again.
You cannot focus a moving subject continuously.
The image brightness may change during and after the AF
operation.
If the light source changes while the Live View image is displayed,
the screen may flicker and focusing may be difficult. If this happens,
exit Live View shooting and execute autofocus under the actual light
source.
When [FlexiZone - Single] is set and you press the <u> button, the
area covered by the AF point will be magnified. Press the shutter
button halfway to focus while in the magnified view. This is effective
when the camera is attached to a tripod and you need to attain very
precise focus. If focusing is difficult in magnified view, return to the
normal display and use AF. Note that the AF speed may differ
between the normal and magnified views.
If you magnify the view after focusing with [FlexiZone - Single] in
the normal view, precise focus may not be achieved.
If [ Live mode] is set, magnified view is not possible.
u
145