Canon RF 100-400mm F5.6-8 IS USM Instructions Manual page 13

Image Stabilizer
The Image Stabilizer for this lens is suited to hand-held shots in the following conditions.
Panning shots of vehicles, trains, etc.
z
It compensates for vertical camera shake during panning shots in a
horizontal direction, and compensates for horizontal camera shake
during panning shots in a vertical direction.
In semi-darkened areas such as indoors or
z
outdoors at night.
In locations where the flash cannot be used,
z
such as art museums and theater stages.
In situations where your footing is uncertain.
z
In situations where fast shutter speed settings
z
cannot be used.
ENG-12