Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 103)

2.
Focus on the subject.
As you look through the viewfinder, aim the AF point over the subject,
then press the shutter button halfway.
After the camera focuses, the focus indicator < > in the lower right of
the viewfinder lights up (in One-Shot AF mode).
The shutter speed and aperture value are set automatically and
displayed in the viewfinder and on the top LCD panel.
3.
Check the display.
Standard exposure is available unless the shutter speed and aperture
value are blinking.
4.
Take the picture.
Compose the shot and press the shutter button completely.
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