Canon RF 400mm f/2.8 L IS USM Instructions Manual page 10

4. Setting the Focusing Distance Range
Focusing distance range selector switch
You can set the focusing distance range with a
switch. By setting a suitable focusing distance
range, the lens is prevented from focusing on a
subject at an unintended distance.
Focusing distance range
Lens
RF400mm F2.8 L IS USM
RF600mm F4 L IS USM
Ranges
FULL (2.5m-∞)
2.5m-7m
7m-∞
FULL (4.2m-∞)
4.2m-16m
16m-∞
ENG-9