Canon EF 400mm f2.8L IS II USM - Manual (Page 9)

ENG-8
5. Focus Preset
By presetting any focusing distance, you can instantly focus at that point even while you are
shooting a different subject. This function operates in any of the AF, PF, and MF modes.
< How to Set >
Press the focus preset
button.
The focused distance will be O O
preset.
If the focus preset switch was
O O
set to , the beeper will
sound once.
Press the shutter button
halfway to focus the
distance you want to preset.
Set the focus preset switch
to ON or . COP
Y