Canon EOS REBEL T3 Basic Instruction Manual page 63

You cannot take a picture during autofocusing. Take the picture while the
Live View image is displayed.
3
Focus the subject.
Aim the AF points over the subject
and press the shutter button halfway.
X
The Live View image will turn off, the
reflex mirror will go back down, and
AF will be executed.
X
When focus is achieved, the AF point
which achieved focus will turn green
and the Live View image will
reappear.
X
If focus is not achieved, the AF point
will turn orange and blink.
4
Take the picture.
Check the focus and exposure, then
press the shutter button completely to
take the picture (p.56).
Changing the Autofocus Mode
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