Canon EOS REBEL T3 Basic Instruction Manual page 214

Changing the Autofocus Mode
If he focus is way off, face detection will not be possible. If he lens
enables manual focusing even while the lens focus mode switch is set to
<f>, turn the focusing ring to attain rough focus. The face will hen be
detected and <p> will be displayed.
An object other than a human face might be detected as a face.
Face detection will not work if the face is very small or large in the picture,
too bright or too dark, titled horizontally or diagonally, or partially hidden.
The <p> focusing frame might cover only part of the face.
When you press <
(p.128). You can press he <S> key to move the AF point. Press <
again to return to the u (face detection) Live mode. (If C.Fn-8 has been
set, press <O> + <
Since AF is not possible with a face detected near the edge of the
picture, he <p> will be grayed out. Then if you press the shutter button
halfway, the center AF point < > will be used to focus.
130
2
Focus the subject.
Press the shutter button halfway and
the camera will focus the face
covered by the <
X
When focus is achieved, the AF point
will turn green and the beeper will
sound.
X
If focus is not achieved, the AF point
will turn orange.
If a face cannot be detected, the AF
point < > will be displayed and AF
will be executed at the center.
3
Take the picture.
Check the focus and exposure, then
press the shutter button completely to
take the picture (p.122).
0
>, the AF mode will switch to the Live mode
0
>.)
> frame.
0
>