Canon EOS Rebel T4i 18-135mm IS STM Lens Kit Instruction Manual page 161

When [Quick mode] is set, [Continuous AF] cannot be set (p.150).
The [Quick mode] cannot be set for movie shooting.
You cannot take a picture during autofocusing. Take the picture while the
Live View image is displayed.
Changing the Autofocus Method (AF Method)
Focus the subject.
3
Aim the AF point over the subject and
press the shutter button halfway.
The Live View image will turn off, the
reflex mirror will go back down, and
AF will be executed. (No picture is
taken.)
When focus is achieved, the AF point
that achieved focus will turn green
and the Live View image will
reappear.
If focus is not achieved, the AF point
will turn orange and blink.
Take the picture.
4
Check the focus and exposure, then
press the shutter button completely to
take the picture (p.144).
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